Chunks can occasionally be misplaced upon loading a world

Can you please attach the game logs from when the chunks started to be in the incorrect place? You can find all game files in .minecraft/logs.

Thanks, that's worth a lot! Can you attach the previous log as well?

This is now the collection ticket for all kinds of chunk corruption issues in 1.15 going forward, as it's very difficult to nail down the exact cause, and even more so if you're not a developer.

Example world file could be helpful

1.15 should be delayed until this is fixed.

It should not, as 1.14.4 has an even more severe chunk dislocation issue. Also, we really need more info if this should be fixed. Game logs from both before and after the corruption would be very appreciated.

It affect 1.15 Release

Affects 1.15.1. My hard work is gone😞

Affects 1.15.1 My render distance was at 32 chunks and I went to spawn. Came back (in one session) and some chunks that were unloaded were glitched. 

I get i my logs the following corruption:

[10:03:30] [Server thread/INFO]: Preparing start region for dimension minecraft:overworld
[10:03:30] [Server thread/ERROR]: Chunk file at [16, -15] is in the wrong location; relocating. (Expected [16, -15], got [16, -10])
[10:03:30] [Server thread/ERROR]: Chunk file at [15, -16] is in the wrong location; relocating. (Expected [15, -16], got [15, -7])
[10:03:30] [Server thread/ERROR]: Chunk file at [16, -16] is in the wrong location; relocating. (Expected [16, -16], got [16, -15])
[10:03:30] [Server thread/ERROR]: Chunk file at [17, -16] is in the wrong location; relocating. (Expected [17, -16], got [17, -14])
[10:03:30] [Server thread/ERROR]: Chunk file at [15, -15] is in the wrong location; relocating. (Expected [15, -15], got [15, -14])
[10:03:30] [Server thread/ERROR]: Chunk file at [17, -15] is in the wrong location; relocating. (Expected [17, -15], got [17, -12])
[10:03:30] [Server thread/ERROR]: Chunk file at [15, -14] is in the wrong location; relocating. (Expected [15, -14], got [6, -3])
[10:03:30] [Server thread/ERROR]: Chunk file at [17, -14] is in the wrong location; relocating. (Expected [17, -14], got [17, -10])
[10:03:30] [Server thread/ERROR]: Chunk file at [15, -17] is in the wrong location; relocating. (Expected [15, -17], got [0, -6])
[10:03:30] [Server thread/ERROR]: Chunk file at [16, -17] is in the wrong location; relocating. (Expected [16, -17], got [12, -5])
[10:03:30] [Server thread/ERROR]: Chunk file at [17, -17] is in the wrong location; relocating. (Expected [17, -17], got [1, -4])
[10:03:30] [Server thread/ERROR]: Chunk file at [18, -17] is in the wrong location; relocating. (Expected [18, -17], got [18, -15])
[10:03:30] [Server thread/ERROR]: Chunk file at [14, -16] is in the wrong location; relocating. (Expected [14, -16], got [14, -11])
[10:03:30] [Server thread/ERROR]: Chunk file at [18, -16] is in the wrong location; relocating. (Expected [18, -16], got [18, -14])
[10:03:30] [Server thread/ERROR]: Chunk file at [14, -15] is in the wrong location; relocating. (Expected [14, -15], got [14, -12])
[10:03:30] [Server thread/ERROR]: Chunk file at [18, -15] is in the wrong location; relocating. (Expected [18, -15], got [18, -13])
[10:03:30] [Server thread/ERROR]: Chunk file at [18, -14] is in the wrong location; relocating. (Expected [18, -14], got [18, -9])
[10:03:30] [Server thread/ERROR]: Chunk file at [18, -13] is in the wrong location; relocating. (Expected [18, -13], got [18, -8])
[10:03:30] [Server thread/ERROR]: Chunk file at [14, -5] is in the wrong location; relocating. (Expected [14, -5], got [17, -17])
[10:03:30] [Server thread/WARN]: Found invalid structure reference [ Mineshaft @ [19, -16] ] for chunk [14, -5].
[10:03:30] [Server thread/ERROR]: Chunk file at [13, -6] is in the wrong location; relocating. (Expected [13, -6], got [15, -6])
[10:03:30] [Server thread/ERROR]: Chunk file at [14, -6] is in the wrong location; relocating. (Expected [14, -6], got [16, -20])
[10:03:30] [Server thread/WARN]: Found invalid structure reference [ Mineshaft @ [19, -16] ] for chunk [14, -6].
[10:03:30] [Server thread/ERROR]: Chunk file at [15, -6] is in the wrong location; relocating. (Expected [15, -6], got [16, -21])
[10:03:30] [Server thread/WARN]: Found invalid structure reference [ Mineshaft @ [19, -16] ] for chunk [15, -6].
[10:03:30] [Server thread/ERROR]: Chunk file at [15, -5] is in the wrong location; relocating. (Expected [15, -5], got [17, -20])
[10:03:30] [Server thread/WARN]: Found invalid structure reference [ Mineshaft @ [19, -16] ] for chunk [15, -5].
[10:03:30] [Server thread/ERROR]: Chunk file at [13, -7] is in the wrong location; relocating. (Expected [13, -7], got [15, -21])
[10:03:30] [Server thread/ERROR]: Chunk file at [14, -7] is in the wrong location; relocating. (Expected [14, -7], got [15, -12])
[10:03:30] [Server thread/ERROR]: Chunk file at [15, -7] is in the wrong location; relocating. (Expected [15, -7], got [10, -22])
[10:03:30] [Server thread/ERROR]: Chunk file at [12, -6] is in the wrong location; relocating. (Expected [12, -6], got [17, -13])
[10:03:30] [Server thread/WARN]: Found invalid structure reference [ Mineshaft @ [19, -16] ] for chunk [12, -6].
[10:03:30] [Server thread/ERROR]: Chunk file at [16, -6] is in the wrong location; relocating. (Expected [16, -6], got [10, -23])
[10:03:30] [Server thread/ERROR]: Chunk file at [12, -5] is in the wrong location; relocating. (Expected [12, -5], got [14, -5])
[10:03:31] [Server thread/ERROR]: Chunk file at [13, -3] is in the wrong location; relocating. (Expected [13, -3], got [1, -2])
[10:03:31] [Server thread/ERROR]: Chunk file at [14, -3] is in the wrong location; relocating. (Expected [14, -3], got [9, -26])
[10:03:31] [Server thread/ERROR]: Chunk file at [0, -20] is in the wrong location; relocating. (Expected [0, -20], got [0, -11])
[10:03:31] [Server thread/ERROR]: Chunk file at [1, -20] is in the wrong location; relocating. (Expected [1, -20], got [6, -7])
[10:03:31] [Server thread/WARN]: Found invalid structure reference [ Mineshaft @ [10, -10] ] for chunk [1, -20].
[10:03:31] [Server thread/ERROR]: Chunk file at [1, -18] is in the wrong location; relocating. (Expected [1, -18], got [10, -21])
[10:03:31] [Server thread/ERROR]: Chunk file at [2, -18] is in the wrong location; relocating. (Expected [2, -18], got [5, -8])
[10:03:31] [Server thread/ERROR]: Chunk file at [-1, -19] is in the wrong location; relocating. (Expected [-1, -19], got [-1, -8])
[10:03:31] [Server thread/ERROR]: Chunk file at [-1, -18] is in the wrong location; relocating. (Expected [-1, -18], got [-1, -5])
[10:03:31] [Server thread/ERROR]: Chunk file at [3, -18] is in the wrong location; relocating. (Expected [3, -18], got [3, -14])
[10:03:31] [Server thread/ERROR]: Chunk file at [12, -19] is in the wrong location; relocating. (Expected [12, -19], got [13, -17])
[10:03:31] [Server thread/ERROR]: Chunk file at [11, -20] is in the wrong location; relocating. (Expected [11, -20], got [16, -11])
[10:03:31] [Server thread/WARN]: Found invalid structure reference [ Village @ [15, -11] ] for chunk [11, -20].
[10:03:31] [Server thread/WARN]: Found invalid structure reference [ Mineshaft @ [20, -9] ] for chunk [11, -20].
[10:03:31] [Server thread/ERROR]: Chunk file at [13, -20] is in the wrong location; relocating. (Expected [13, -20], got [14, -9])
[10:03:31] [Server thread/WARN]: Found invalid structure reference [ Village @ [15, -11] ] for chunk [13, -20].
[10:03:31] [Server thread/ERROR]: Chunk file at [13, -19] is in the wrong location; relocating. (Expected [13, -19], got [13, -16])
[10:03:31] [Server thread/WARN]: Found invalid structure reference [ Mineshaft @ [10, -10] ] for chunk [13, -19].
[10:03:31] [Server thread/ERROR]: Chunk file at [12, -18] is in the wrong location; relocating. (Expected [12, -18], got [12, -14])
[10:03:31] [Server thread/ERROR]: Chunk file at [10, -21] is in the wrong location; relocating. (Expected [10, -21], got [8, -7])
[10:03:31] [Server thread/WARN]: Found invalid structure reference [ Mineshaft @ [10, -10] ] for chunk [10, -21].
[10:03:31] [Server thread/ERROR]: Chunk file at [14, -21] is in the wrong location; relocating. (Expected [14, -21], got [15, -20])
[10:03:31] [Server thread/ERROR]: Chunk file at [10, -19] is in the wrong location; relocating. (Expected [10, -19], got [11, -20])

I have experienced the same problem on my server.

Somehow the order of the chunks in the region file gets mixed up. In the chunk itself the correct position is still stored until the chunks are loaded. Then minecraft goes like you are standing in the men's toilet queue and even though you tell me that you are a woman you have to be a man because you are standing in the men's toilet queue.
So minecraft says chunk your data is wrong you actually belong there although the chunk is actually right.

But i have no idea what happens to the chunk actually at that position in the file.

Anyone who has experienced this chunk corruption should post a world save in a zip file along with the logs. Region files that are not affected can be omitted to keep the size down. It's usually only one region file that is affected.

The basic structure of an MCA region file is a header in cluster 0 that points to the chunk data and indicates its length, another header in cluster 1 that stores the time of last modification, and then the chunk data from cluster 2 onwards. A cluster is 4096 bytes.

When writing the chunk data, the headers and data must both be written. These are separate file I/O operations and this is where problems can occur if it is not done correctly. The wrong way to write the data is to write the headers and then the data. If the data is not written (eg: a crash), the headers point to the wrong location and the data can be lost if the headers are changed. The correct way to handle this is to write the data first (to an unallocated place in the region file) and then update the headers. If there is a crash here, the headers will still be pointing to the old data.

For this particular issue, another problem may be the cause. Each chunk in a region file stores its global chunk coordinates as xPos and zPos. If the headers are pointing to the wrong chunk, the coordinates in the chunk are much more likely to be correct. It is possible that the chunk's coordinates are being ignored and the game is attempting to fix them by assuming that the headers are correct.

What the game should do if it detects misplaced chunks is kick all players, close the world, mark it as needing repair, and not allow players to enter the world again until the game has repaired the problem as best it can. Repairing the problem would be done in a similar way to how players can Optimise a world, and it can be done for any world. Repairing requires the game to inspect every region file for correctness, and if it finds an incorrect region file (any header doesn't point to the correct chunks) it goes through every cluster of the region file to find the actual chunks and then rebuilds the headers as best it can. If it cannot find a chunk for any reason, it can either search the Backups folder for older copies of the world, search a player-specified location for backups, or delete the chunk and make the game regenerate it. The locations of backups for a world can be stored as a JSON file in the world save and can include player-created backups. External tools like Region Fixer can already do this.

I had this isusue too it apears when swiching worlds. lets say u generate world a and swich in no time to world b.
then b world gets corupted.

If you wait before swiching worlds, nothing bad happens.

Happened to me too, we lost a Community base due to this bug and some server members lost valuable items.

We even had a newcomer that suddenly came in and saw the destruction.

I will ask the server owner to put the world zip file in there, not sure if it will work or change anything, no harm in trying.

This just happened to me, the affected region is r.6.-1, here is the world file: 

I also made a thread with more info on the issue, not sure if I should link these here but I will anyway

https://www.spigotmc.org/threads/region-file-gets-corrupted-when-added-to-the-server.417990/

Are your sure you have enough diskspace?

Can someone check if this bug occurs in 20w08a ???

Can someone help me? My world is having the same issues and I'm getting no help even though I'm posting about this everywhere. I have put a lot of effort into this world, how am I supposed to fix it?

I'm having this issue as well.  There was a power failure, but the game wasn't running at that time.  So I bet (but am not 100% convinced) it's unrelated.  We did not have a backup which I'm kicking myself for.  I've narrowed it down to one region file.  I found the log, both are uploaded here: 

Affecting me too. I am new-ish to Minecraft and unfortunately don't have any backups. Have they released any possible fixes?

There is a fix to it, but with a minor inconvenience. If you have the seed of the world, you can create a copy of the world, try to find certain chunks, and then replace the broken chunks with the old ones there previously. Unfortunately, this will make it so any thing created after world generation will be gone. Blocks, mobs, chest, everything. If you are playing on a server, it could be a server problem, just like the problems in 2b2t, though that is near impossible. It is mostly just caused by low or faulty storage.

This issue only seems to happen when Minecraft closes unexpectedly due to the system shutting down (i.e., power outage). I don't think I've seen a report where this wasn't the case. Correct me if I'm wrong.

It also seems to happen when you load one world, exit it and load the next world immediately after, without waiting (jokubas' comments), probably while the first world is still being saved or internal data structures not cleared yet. Also when players logged into the same world twice at the same time, at least once via singleplayer, e.g. MC-173080.

So, if I understand correctly, there is no way to recover  the chunks to their previous state (builds included)?  My inventory is completely gone, the village I created is decimated, my castle is now in five different places, and I just defeated the dragon yesterday and no longer have the dragon egg or shulker boxes.

Not a funny April Fool's joke.  At.  All.

Has there been any progress on fixing this issue?  

20w14a introduced some tweaks to chunk saving which should hopfully cause this issue to happen less often:

Region files are now opened in synchronous mode to prevent data loss and corruption after crash.

• ​Dedicated servers can disable that by changing sync-chunk-writes inside server.propeties

https://www.minecraft.net/en-us/article/minecraft-snapshot-20w14a

puedo hacer algo para restaurar mi mundo si no tengo backup¿?

@jacob gomez sanchez, you can speak only English

Translation of Jacob Gomez-Sanchez's comment: Can I do something to restore my world if I don't have a backup?

@jacob gomez sanchez

No. You can't, unless you like to play with the puzzle.

Opening the files in synchronous mode may cut down on the number of times this issue happens, but it won't fix the problem where the chunks are being shuffled.
From the sample log provided by Rens Haakman:
[10:03:30] [Server thread/ERROR]: Chunk file at [16, -15] is in the wrong location; relocating. (Expected [16, -15], got [16, -10])
Here, Minecraft has found the chunk pointed to by the headers is not correct. Although it's not clear what's happening here, I think Minecraft is attempting to fix the problem by changing the chunk data to match the headers. If this is what it is doing, this is wrong. Very wrong. There is no reason to suspect that properly-saved chunk data will suddenly become incorrect while the headers are correct. There is every reason to suspect that the headers have simply ended up pointing to the wrong location. This means the correct chunk data could be lost somewhere in the file, and it is important to find it before it get stomped.
It turns out that the headers in an MCA file are redundant. The data parts of the region file contain everything except the timestamp of last modification (though the chunk data contains a modification timestamp in game time). The headers only exist to show where the chunk data is, how big it is and when it was last modified. The chunk data starts with the exact length of the data, and the chunk data itself includes the coordinates of the chunk. The headers could in theory be rebuilt using nothing but the chunk data.
The first eight bytes of chunk data for each chunk are 4 bytes for the length (in big endian format), the encoding (usually 02 hex), and if the encoding is 02 then the next three bytes are a ZLib header (always 78 9C ED hex). It should be possible to scan each chunk, and if the scan finds the magic number "02789CED" starting 4 bytes from the start then it could mark this as a possible starting location for a Zlib chunk. These possibilities can then be opened, decompressed and scanned and if no exceptions are thrown or other errors found such as NBT errors then it's a viable chunk. The newest chunk candidates in each location (duplicate chunks are fairly common in region files) can be written into the headers as the chunks.
Other encoding formats are possible. Handle these accordingly.
This kind of deep scan won't find every single lost chunk, but it would do a good job. (A caveat: if chunks are "deleted" using external tools they may remain in the file and would be resurrected.) It is easier, however, if people remembered to back up their worlds periodically.

Yes, the exact same error occurred with me, it's really annoying.

• MC-178145

I hope for both of us that the error will be fixed soon.

This happened to me to when i forgot to save my world

Can confirm increasing RAM does NOTHING, we switched our server from 2GB to 12GB and corruption still happened

But guys, how do you fix it

In the same boat, well I was until a bunch of chunks threw me out and destroyed my World...no solution yet?

@Daan Kuster The only way to fix it is by having a backup of the world or region file. If you have no backup you could try to reposition chunks manually but it is very likely that many chunks are completely missing(overwritten) in the region file. Here is an image of my world xD: https://prnt.sc/s49j2b

Happened to me as well. Hopefully the issue gets resolved soon

Just happened to me today. Lost about 30 hours of builds 😞 No power outages either. I have two zips of the same world, one old backup that is not corrupted as well as the current one which was corrupted. How can I upload them?

In my world chuncks didn't just delete but they got relocated to other chunks nearby destroying most of my buildings everything just looks ugly. when i try to fix it using region fixer or something it doesnt work. It simply doesnt see the relocated chunks as corrupted and therefore I can't fix it. please fix this problem or make something that can return the chunks to the right place.

This bug scares me, I don't want to play the game with this happening being a posibility!

Take backups regularily, and you can just restore from a backup.

For the record, this issue seems to be more common if your volume is already quite full, Minecraft unexpectedly shuts down (i.e. power outage), or if you run multiple instances of Minecraft at once. If you do neither, you'll probably be fine. Still, take backups (that should always be done anyway, if you care about your world).

And as was already said, there were some changes in the 1.16 snapshots that mitigate this issue at least by no longer writing the save files asynchronously, among other things.

I believe I'm getting the same bug. I've restored the affected regions from an older version repeatedly, and every time it loads, it just does the same thing, with the same chunks being corrupted/removed. This particular area is old, from when I first created the world (back when Large Biomes were first introduced) and I haven't changed it much over the years, so it's possible that it's targeting older chunks. But then, it's more difficult to notice on newer ones that match up with the newer terrain generation. I've uploaded a couple screenshots of my corrupted area.

Additionally, I have tried the 1.16 snapshots and encounter the same issue.

This has just started to happen to me. In about 5 minutes about 10 -20 chunks suddenly appeared incorrect, making random outcrops of mountain, destroying buildings, some buildings being reproduced  in bits in other areas, almost like chunks are being randomly copied and pasted in other areas. How do I stop this and put everything back to how it was?

I'm not sure if this is related, but we've had disappearing block in 1.15.2 (see attachment)

That doesn't seem to be chunk corruption. My guess is that it was caused by fire; there's the lava lake nearby; perhaps some of the tall grass caught fire and it went up the side of the building. Or else it might have been struck by lightning.

I just confirmed that my issue has been fixed with the release of 20w21a. Looks like it was caused by MC-181522. Restoring a backup or copying the affected regions from a backed up save successfully restored the corrupted chunks, and they seem to be staying that way.

If i haven't back up the world, can I still get the original back?

'Fraid not, friend. Always back up your worlds.

how do you back up your world?

In newer versions of Minecraft, you can easily create a backup by selecting your world in the singleplayer screen, clicking on "Edit world" and selecting "Make Backup". Then a backup is automatically created in .minecraft/backups, which you can also open by clicking "Open Backups Folder" in the same screen.

the same happend to my world

I didn't back up because I didn't know about that option. How to restore?

You can't restore a backup if you didn't make a backup...

Can anyone reproduce this on a world that has never seen any kind of modification usage (any kind of modification, this especially includes Optifine), or even potentially a third party program (such as NBTExplorer or MCEdit)? The lack of reports we have so far received for 1.16 either indicates that this was fixed, or that this was caused by third party programs or tools not yet available for 1.16.

This happened to me twice on a server once on 20w21a (vanilla server with fabric and carpet mod) and once on 1.16pre1 (vanilla server jar).

vanilla server with fabric and carpet mod

That's by definition a non-vanilla server.

 responding to - [mod]violine1101In newer versions of Minecraft, you can easily create a backup by selecting your world in the singleplayer screen, clicking on "Edit world" and selecting "Make Backup". Then a backup is automatically created in .minecraft/backups, which you can also open by clicking "Open Backups Folder" in the same screen.

Hi I did this but how do I then revert back to the back up? I tried double clicking the zip folder, and it opened it but no idea what to click on next??

Copy the file inside of it into your .minecraft/saves folder.

Edit: I've also heard that mcaselector, a tool for managing and deleting chunks in a Minecraft world is also capable of swapping chunks in order to fix worlds affected by this. I've not tested this myself, and don't take this as an official recommendation, but here's a link to the tool: https://github.com/Querz/mcaselector

That's by definition a non-vanilla server.

I am aware and as pointed out I also experienced this bug on a more recent version of Minecraft on a Vanilla server. Will report if it happens again on 1.16-pre3 or later I hope it has been resolved.

Replying to - 'Copy the file inside of it into your .minecraft/saves folder.'

Err which file?

Wouldn't it make more sense and be a lot easier if the backup was automatically accessible via the games UI. Or better yet just be able to save whenever you want, a rather basic function that pretty much every other game in the world seems able to do.

Also how do I officially reply to a comment? like above they've linked to the comment, but I cannot seem to find any option to do that.

here's mine! its gone!!!

@sam craig: DO NOT do that ever again, you just uploaded over 200 files which all had to be deleted one by one - please instead provide a .zip folder hosted on a third party host if you want to provide your world.

Hello there. 
This issue just happened to me last night! I've just attached the logs and some screenshots I've taken. [See files: 

]
The very first one was taken by accident, but it serves to show the chunk that disappeared; in one of the others you can see a floating scaffolding block, which was attached to a scaffolding tower that I'd build, all the way to world height, but I couldn't find that piece of terrain anywhere now. 

Except from that, all the other errors seems to be the chunks relocated with one another.

Your can clearly see in the log "

" pieces like: 

— [01:46:59] [Server thread/INFO]: Preparing start region for dimension minecraft:overworld
— [01:47:01] [Server thread/ERROR]: Chunk file at [-7, -6] is in the wrong location; relocating. (Expected [-7, -6], got [-6, -7])
— [01:47:01] [Server thread/ERROR]: Chunk file at [-6, -6] is in the wrong location; relocating. (Expected [-6, -6], got [-2, -6])
— [01:47:01] [Server thread/WARN]: Found invalid structure reference [ Mineshaft @ [4, -6] ] for chunk [-6, -6]. 

But I couldn't find anything relating to memory leakage or such.

I should point out that that log is after the error happened, which seems to have taken place before and cause the computer to crash, and that log is the immediate login after. 

Hope it helps. 

soNin_MC

I have this problem too

I think its from the launcher

MC-188398

is there any command for changing the chunks position?

Confirmed in 1.16 Release Candidate 1.

I see someone has put a solution at the top, but I before I risk trying that, I am still waiting for someone to explain to me how I restore a backup world...

Can anyone reproduce this on 1.16 using absolutely no mods on a world that has not been opened using any mods or third party tools?

Got confirmation of this happening in worlds that were not opened with any mods or using any external tools.

replying to  [Mod] Galaxy_2Alex - "Can anyone reproduce this on 1.16 using absolutely no mods on a world that has not been opened using any mods or third party tools?"

Yes mine is mod free and 1.16 and I think lots others on this thread have said theirs is aswell

I reproduced this bug on Snapshot 20w22a. where a layer of water generated at y=59 under a floating village.

We are having the same issue on our 1.15.2 Spigot Server. The world is relatively old and we also encountered the problems in an older version a time ago. (It was one of those unstable ones... dunno, 1.13 or 1.14?). The last time we restored a backup.

But now the problem is there again. One chunk gets replaced by another one. We found it by chance, so we got no clue what triggered it (We changed a good many biomes tho... maybe that is some issue? Strangely the chunk error is in a whole different area, where we didn't change anything.

The thing is, I wouldn't mind to restore one or two chunks. But to me, it looks like it is spreading. (It also did the last time it happened: First only a few chunks were corrupted, but they became more and more. And putting the chunk from a backup in the broken ones place didn't help much; soon after it swapped again.) So this time, we found one broken chunk and replaced it. And now I found another one... I will load a backup again.

I really thought this one got fixed with 1.15.2... It is quite annoying, because last backup is a few weeks old. And very often you don't find the broken chunk immediately...

I am kind of afraid of corrupted worlds... (I can't provide any log i fear, since i don't know when it happened)

The first time I decided to look this up, we just lost our 3rd base due to chunk corruption.

First our Main base where everybody comes together, then followed the Community base where new people spawn in, then I noticed a lot more chunk corruption at a place where nobody has build yet, which I took screenshots from and posted in here, not that they'll add to what already is here and right now today, last but not least the Igloo a friend build where I personally live nearby had a single chunk corrupted which broke apart a long rail road system around 8000x3000, it is replaced with gravel & water.

We play on a server completely vanilla, absolutely no mods, no third party tools, no datapacks, just vanilla, we don't even have Automatic farms to get us infinite resources.

I am out of words as we may have to restart our world from scratch, square one.

The kids and other family members who play on it are going to be devastated

Since I am posting this might as well try to inform on a pattern that I noticed, it seems to happen more often and more quickly after each other, as if more corruptions seem to appear in a faster pace and it always seems to appear after a crash.

25 January 2020 - Main base corrupted.

5 June 2020 - Community base corrupted.

30 June 2020 - From the screenshots. (Kirsi's exploration)

11 July 2020 - Igloo (Igloo's storage unit) + Rail road.

I don't know if this information is valuable, I just felt like sharing it, who knows it could be of any use to find out a solution or how it works.

Can confirm this happened to worlds hosted on Realms in 1.15.2, haven't seen it in the month since then but may still affect Realms worlds

We've just started our new world (Vanilla last the last), currently settling down, and in about 2-3 days, we got our first corruption in our new world.

Having corruption in a world, size over 3 GB, annoying but understandable, this is brand new started up 2 days ago.

Leaving a screenshot above.

hey Marilyn

from your screenshots, it doesn't look like "misplaced" chunks, but instead, chunks generated using a different seed.

but since you say "2 days ago" that isn't a thing that should happen (no update since then)

I will say that I've been experiencing Chunk misplacement issues since 1.15. So far, there's been a total of 10 chunks that are randomly swapped in my Multiplayer world. I also experienced a ton of lighting bugs on my world where a bunch of dark rectangles are in the world. The world has been converted from 1.15 to 1.16

I have experienced this issue almost as long as I have played minecraft. I started in 1.6.4 and I think those worlds are gone now but, i have some worlds from very early 1.7.2 that had horrid chunk glitch issues as they updated. The center of the castle in my avatar pic was regenerated to original chunk. I have also noticed some odd chunk overrides where the natural chunk is replaced by a weird ass biome. For instance, there is a single jungle biome that almost killed me in one of my 1.7 based survival worlds when i was walking in extreme hills. There is also some odd chunk borders in some areas where it looks like one stlye of chunk stopped generating and a new style of world generation began. there is a definate MASSIVE ring around certian arras of my 1.7 worlds where the chunks just decided to start making new biomes.

@smaugthegreat108 Minecraft 1.8 change how minecraft generates chunks, so all worlds behind that if upgraded will change biomes and generate ugly borders. Your comment has nothing to do with this bug.

This did happen to me actually about a month ago. This is most likely a bug.

Thanks Sherlock

how do we reproduce this?

To reproduce, I got a blue screen of death with the stop code of ATTEMPTED_EXECUTE_OF_NOEXECUTE_MEMORY which I got while running a server and playing Minecraft at the same time. Has happened twice now.

this bug is caused by corrupted worlds

basing on MC-216158, still happens on 1.16.5

I get this issue whenever i try to upload my world from 1.15.2 to 1.16-1.16.5. I have never encountered this bug in 1.15.2 for some reason. 

still happens in 21w05b

it just happens to my world

Is this still an issue?

Not for me anymore

Still seems to occur in the release of 1.18, i have a server world all the way from 1.12.2 and converted it to 1.18, all in steps with each version in between. Loaded some old chunks that havent been loaded since the world was taken from the server and they seem to generate completely new terrain overwriting old terrain, including buildings. Its such a shame that this is happening, considering i have been using it as my personal main world ever since and every chunk within 15k had been pre-rendered for the server before that.

That's a different issue then. This one is not related to upgrading and also not about regenerating chunks, but instead about them swapping positions.

Can you link open cases fitting the description of my bug? Would appreciate it, thanks.

I actually can't find any. Report it, attach the world (preferably a backup from before the issue happened) and maybe a moderator will find a duplicate or it is actually a so far unknown issue, which is even better.

For pre-1.12 chunks failing to load, MC-239962 is probably best bet.
So far it seems to be mostly caused by WorldEdit.

My easiest solution to this fix is ignore the chunk error and instead make a backup of the world every time we log out and overwrite the 3 previous backups when we log out of the world the next time and if it sees an error log output during loading the world then warn them to go back to the previous version to load this world and after that load the backup but if that backup also gives a chunk error output load the previous one and warn them to switch to previous version after that and if that also fails then the world will load on its own and with chunk error