Fenced Animals, Villagers, and other mobs disappeared.

Upon further testing chunk loading and unloading seems to be the biggest culprit of missing mobs. The only time I lose mobs while saving and exiting is when the game loses communication and gives the communication error message.

It sounds like your problem is the communication errors then, doesn't it? If those are involved, that problem needs to be fixed before we can even consider whether the game has a bug. The game depends on having reliable communication. If it's sporadically failing, the possible effect on the game is unpredictable, so it's impossible to say whether what happens is a bug in the game.

I didn't realize earlier that you were on a Switch. There's no way to make a backup world copy on a Switch, right?

You can only export a world from Switch if you have a realm that you can use to upload, and then a PC or mobile device to download the realm world from.

The "communication error" on Switch is from the Switch OS and, in my experience, it usually means the Switch has failed to connect when trying to use a function that requires internet connection. I'm not sure why that would come up when exiting a world, unless perhaps if the world is using marketplace content or there is an issue with storage space and cloud backup on the Switch. If Minecraft is triggering the error that could be a bug. I don't think it is the same as a crash but it could conceivable cause a problem with saving world data.

Sara, can you think of anything that may be triggering the communication error? Does it give any further detail like an error code? Does it dump you to the Switch home screen (which would seem to be a crash)?

It does not give me an error code when the communication error occurs. I've been paying vanilla the only marketplace content might be my character's clothes. If you leave your game running but unattended too long it will trigger a communication error or if the internet goes down. No idea why leaving it set does this either because nothing happened to my internet while I let it sit and it only happens in Minecraft. I've left other games running and it doesn't disconnect from the internet. When it errors out the game doesn't crash and appears like you can still play but if you save and exit it may or may not have saved correctly and that's when the mobs go poof. As a side note the marketplace and dressing room on the Switch is rough and doesn't load correctly since I've owned it. They have massive loading issues.

Is this the same issue as we're reporting on MCPE-144208, and if so, should our reports go here?

The current status of this issue is complicated. We closed MCPE-144208 because after a couple of fixes were applied, the Mojira staff are no longer able to reproduce the issue. From the number of comments since then, however, there is clearly still something that needs fixing.

Normally, we would reopen 144208, but we aren't going to do that this time because of the hundreds of repetitive comments in it that provide no useful information. Instead, we're currently waiting for somebody who can create a new report following our guidelines. The guidelines instruct you to tell us how to reproduce the issue, which is something nobody has done up until now, which is why this issue still hasn't been fixed for some of you. So to answer your question,

• This is the same set of symptoms as MCPE-144208, but it's not the same issue because it has a different cause.

• We don't currently have a usable report of this issue and cause that tells us how to reproduce it. We are waiting for somebody to write such a report, which we will then make our tracking report for the issue.

• If writing a report to the standards given in the guidelines seems like more work than you want to do, leave it for somebody else. 90% of reports don't include the information called for in the guidelines, but we accept some of them anyway if we can figure out how to reproduce the problem on our own. However, we've already tried to reproduce this problem and failed, so we have to let you tell us this time. It you don't follow the guidelines, we won't be able to do anything with your report and your time will just be wasted.

• The recent comments on MCPE-144208, including the one you left, are not useful and should not be reproduced on this or any other report. They are "me too" comments that merely repeat what others have already reported. Comments should only be used to add new information for the devs. If you don't have any new information, you should upvote the report and not leave a comment at all.

Finally, I have responded here because I hope not only you but others will read this and understand why this issue is currently at a standstill. In the future though, you should only use comments to add new information for the devs. Questions about how to write, use, and understand bug reports or why we do things the way we do are considered off-topic here. Instead, we have two places you can talk to us about these matters: The Mojira Discord and the r/Mojira subreddit. Links can be found in our FAQ (part of the guidelines).

I am working on my end to produce a better bug report according to the guidelines. The frustrating aspect of this bug is that there are not always a consistent set of steps to recreate this bug. I am still working with my Nintendo Switch so I am limited in other respects as to what evidence I can share. Please bear with me. I am working as best and as fast as possible. The issue seems to lie within how the game's memory system works. The most consistent results I'm getting at this time are as follows. When I leave my home chunk to gather resources or whatever for anything over about 10 minutes and then return to my home chunk naturally spawned mobs and some and/or all of my fenced mobs etc. may have been purged. It does not occur every time but I have noticed if I've been out doing a lot or picking up a lot of items it happens more frequently. As to when it happens after I've saved and exited or had the communication error I have not been able to get as often. It seems to occur at these times if I've interrupted the game during an autosave. Either way what I have not been able to determine is if there is a communication interruption going on with the memory or if the Switch's memory limitations are being overloaded possibly too much info all at once and/or trying to save as much space as possible. I apologize I haven't been as quick or as neat with my reporting but I'm doing my best to gather the info you need. Thanks for your understanding and hard work team.

@unknown: I appreciate your dedication and understand the difficulty you're having. I thought about addressing you about this report in my previous comment but decided to wait and see if you were still interested and ready to be further engaged.

When I suggested to you in MCPE-144208 to create a new report, I wasn't aware that you were on a Switch. You're right, that's somewhat limiting for the purpose of creating the ideal bug report, and in fact you may not have the ability to give us everything we need. It might be that we'll have to wait for somebody who can reproduce it on Windows or Xbox. But the information you've given us here has been helpful nevertheless. There seems to be a pattern developing that interruptions, either in the game or the network, might be involved, and that could explain why the staff haven't been able to reproduce the problem since we usually test in local single player mode.

So to the extent that you can and want to continue testing for us, please do so and keep up informed of anything new you notice, especially anything that you can reliably reproduce by opening a saved copy of the world. It's not impossible that you could tip the scale and this could become the ticket that smashes the obstacle that been in our way. But don't kill yourself trying. There are lots of other people having this problem apparently, and some of them must be using a platform that's more conducive to the necessary testing. Thanks again for hanging in with us.

I'm playing a single-player world on a Switch and having these issues. The game is behaving as if it were clearing untouched naturally spawned mobs in a newly unloaded chunk but it's not just clearing untouched mobs. The biggest commonality I can find is that to some extent we all use some amount of cloud-based computing/saving. I see an uptick in issues when autosaving and/or the game is using this cloud service heavily. The game is doing what it is designed to do to save memory and computing speed just with the wrong mobs and such. I can't decide if 1. it's a coding issue (Being mobs are not the only casualty I'm less sure of this one. Unless armor stands are a mob?), 2. the cloud is shedding because it is getting overloaded in some way, or 3. some combo of 1 and 2.

I've removed the screenshot of the home screen because it showed your gamertag. I didn't think about that when I asked for it, I was just trying to be absolutely certain of the version number.

Armor stands are indeed entities and part of the same portion of world data as mob(ile) entities. It helps to know that they are affected by this problem, because that confirms it is not related to mobs walking across chunk borders between saves.

Acting more like the memory is being throttled or capped in some way causing fenced mobs and such to be dropped like free mobs are cleared as part of how the game operates. The heavier the processor and memory are used the worse it starts clearing entities. It's just some of those entities I wanted to stay. Fenced, in a house, no where is safe from the cleaning. There is one mob that is populating when things start going missing and it's the wandering trader llamas. No trader just the llamas. I've got half a dozen in the cave under my house and the minute I see new ones I know something at my house has gone poof.

@GoldenHelmet I am on Android and having this issue. In fact, this is also affecting the realm I'm part of. I'd have 30 sheep fenced in spanning 3 chunks and I come back online to a mere 8. This has also reduced my tamed cats. Had 1 of every skin, came back on to only 3 cats total. I will see if I get a clip of the bug for you.

This has had an effect on redstone clocks as well. Given chunks refused to unload, I did catch my grinder's clock lost items (again). And given they are considered as an enity in some cases, I have a clip of it.

Vanishing Enities

Note from @unknown: I edited the link to correct the URL.

And the moment that clip finishes it's upload, sheep vanish again.. Both clip and the following pick were taken on a Realm.

@unknown: Your hopper clock must have lost blocks for a different reason, because items in hoppers are not entities (or mobs, obviously). However, your second comment (that uploading the clip to Google Drive, outside the game may have caused mobs in the game to disappear) could be a very useful clue if it's reproducible. If you can make something like that happen again, please comment again with the details.

@Auldrick I literally just hopped off the Realm a little bit ago as my device battery was low. After reading your reply afterwards, I waiting a few minutes (ensuring chunk unloads), then got back on to check sheep (which I did breed while on as I am using wool as a build outline). Here is the new screenshot. Most vanished again. There was ~19 in the first screenshot sent. Now (even after breeding), I'm down to 12.

@Auldrick I literally just hopped off the Realm a little bit ago as my device battery was low. After reading your reply afterwards, I waiting a few minutes (ensuring chunk unloads), then got back on to check sheep (which I did breed while on as I am using wool as a build outline). Here is the new screenshot. Most vanished again. There was ~19 in the first screenshot sent. Now (even after breeding), I'm down to 12.

Etanarvazac: your screenshots can't be explained by random mob loss. Are you sure another player isn't breeding and killing in your sheep pen? Or that you have your pictures in the right order?

For the issue with the items in the hopper clock, it is no doubt related to the hoppers being in positioned across a chunk border (X = 1663 to X = 1664). However, as Auldrick mentioned, it involves a different part of the game functionality from entities, so it should be reported in a separate ticket.

This is happening non stop on my realms - the last 3 times I have logged in I only have 2 adult villagers and the rest are gone. They are named and traded with every time. Same with a golem. I am now on my 9th time making and naming a golem only for it to be gone when I log in. I am paying money for this to not be fixed.  

Reply from @unknown
Please see REALMS-10040 for mob/entity disappearance issues on realms.
However, please only comment if you have new information related to reproducing the bug.

@GoldenHelmet I'm sure it's not a player. There are 4 of us on there and we are all 1,000+ blocks away. Only meeting point is the center (world spawn) which is linked by NPC's (and don't teleport players to bases that aren't theirs). And the pics were taken & uploaded here an hour apart from the other. I'll get back on, breed more, take screeny, then leave the area for a bit. Will post update later.

On another note, I'm not sure why my last reply duplicated...

As for the clock, I'll check chunks to see if rides a border. If not, I'll look for a report here.

First, I must apoligize for the late reply. Something came up. I was just on the realm a little bit ago and I'm down to 16 sheep (from 29, see screenshots). These are not counting any outside the fence.

Edit: These screenshots are in the 1.18.12 Hotfix

3.1

3.2

--It has been reasonably suggested (in REALMS-10040) that the issue no longer happens to mobs spawned since 1.18.10, though it can still happen to mobs spawned in earlier releases when a player reactivates the chunks they're located in. It's perhaps not a coincidence that these latest screenshots show that all the sheep that disappeared were in one half of the pen, and that that half contains a chunk with no sheep in it. Is it possible that the sheep that disappeared were spawned before 1.18.10?--

--If this theory is correct, it will probably not be possible to prevent more mobs spawned in 1.18.2 or earlier from disappearing, but replacement mobs you obtain from now on would be immune.--

Update:
I misunderstood what was being said on REALMS-10040. Please disregard this comment.

@Auldrick All off my screenshots have been 1.18.10 & 1.18.12.

Edit: In any case, hopefully 1.18.20 does resolve this. However, the release has yet to reach public level.

I have been testing further on the Switch and moving things around on my house area. Keeping animals in smaller pens with only 3 to 4 blocks of movement in either direction has reduced the number of times they disappear. Culling the growing Wandering Trader llama pack in the cave under my house has also reduced the number of penned animals disappearing. Every time the Trader moves across the chunk border he leaves behind his llamas. So I have to cull them frequently but at least I now know why I found so many of his llamas and where he went. I moved where I was placing armor stands and they have stopped disappearing. So I may have placed my house across a chunk border without knowing. It's hard to tell on a Nintendo Switch. Anything that reduces the strain on the memory and processor reduces the amount of unwanted culling of fenced mobs. 

Sara, that is excellent evidence that your issue is the known one caused by mobs crossing chunk boundaries. It's the weekend now, but I'll be sure to discuss it with the other moderators tomorrow.

Why is it difficult to tell where chunk borders are on a Switch? If the integer part of a block's coordinate is an exact multiple of 16, there is a chunk boundary between it and the block to its west (X coordinate) and/or north (Z coordinate). Are you unable to show coordinates for some reason?

So I was right on the money, given my pen crosses 3 chunks.

@Sara Look at your cords. X: 0 Z:0 Always represents the start of a chunk. So if you place a torch at 0,0 and then one every 4th block, the next chunk is evey 4th torch placed. If you look at my screenshots, this is a method I use all of the time. If you are as far from spawn like I am in those, start calculating multiples of 16 on a calculater until you reach your cords (X and Z, seperately). Also, there are tools out these that when you input your seed, it will show your chunk borders.

Edit: Also, if memory stress is the issue, I would recommend as (at least during the issue), that on the edit world screen, changing Simulation distance to 4 chunks (lowest setting).

It's more difficult because unlike the Java version you can't just pop open a visual grid display on the fly and must use math to find and remember the multiples of 16. 

@Sara Very true. That is one thing I used regularly on Java. The math of the method outlined is only if you're far from 0,0. I usually double until I reach the cord I need. For example with 1693: 16, 32, 64, 128. . . 1024 (then less based on prev multiple) 1536 (+512), 1664 (+128), 1696 (+32). So I know 1696 is on a border.

I've mapped my animal pens with torches just to keep things straight using @Etanarvazac 's suggestion. I'll continue to check and see if the animals stop disappearing altogether now that I've fenced them in such a way as they can't cross any chunk borders. I have left 2 small mine carts running across the chunk borders to see what if anything may occur there.

Looking at Etanarvazac's screenshots, two things stand out.

• The large building in the background of 3.2 is not there in 3.1.

• The remaining sheep are all in the right hand side of the long pen.

Counting by the torches, it looks like the building is about 3 chunks away from the sheep pens. Assuming simulation distance 4, that means that the chunk that contains the sheepless left side of the pen probably came in and out of simulation distance many times while the building was being built. I therefore suspect that repeated unloading and loading of the chunk has something to do with entities in it not being saved.

A couple of questions based on experience with past bugs:

1. Is this world with the poofing sheep the Realm you mentioned, or a locally hosted world?

   1. If it's not the Realm, are you the host?

2. For the play session when sheep were lost

   1. Did you initially load in in the end or nether before coming to the overworld?

   2. Were other players logged in to the world at the time?

@GoldenHelmet The build was built after taking the 3.1 screenshot. I just got busy with some other junk and didn't get back to it (3.2) for a little over a day. There are indeed 3 chunks between. The build does go back another 2.5 chunks. So I must agree with you on the constant loading and unloading of chunks.

Answers:

1. Realm is hosted by a friend, and yes, the simulation distance is set on 4.

2. Play session:

   1. Each screenshot (1-3.2) have been mainly overworld. Between screenshots 1 & 2, I made a brief Nether trip to fill buckets for lava, but that was initially loaded in from overworld then Nether, and back.

   2. Due to friend's internet, I've been the only one on between all screenshots.

After Windows 10 Bedrock v1.18.30.20 Beta update, all my villagers and iron golems disappeared from the village. Floating around the village and world are baby villagers and cats.  I picked up several of the baby villagers in a boat, and I took them to the village. They disappeared after I left and returned to the chunk that contains the village. The village has a total encompassing wall.  I have not had an issue with the wholesale disappearance of villagers until this update. If I import a world created in the previous version, the villagers are all present in the aforementioned village. 

Etanarvazac Revorix: Thank you for the additional information. We are trying to keep issues with entites not saving on Realms separate from entities not saving in local games for, to see if can isolate some more specific factors or steps. Please follow REALMS-10040. You may add the details from your last couple of comments over there.

Bubba Doodah: Please see MCPE-152893 for the new issue with floating mobs in 1.18.30.20 beta. I think we can assume that all of the issues you describe are due to that new bug, which is more of a desync than the problem with saving entities that we are tracking here.

If you have a copy of the world available, you might like to upload a copy of it for investigation.

• On Windows 10 you can use the Export world feature.

• On Android or iOS you need to use a file explorer to navigate to Device storage > games > com.mojang > minecraftWorlds

• On Xbox or Switch the only way is to upload it to a Realm, and then download the world on Windows 10 or Android/iOS. (Please do not purchase a Realms subscription just to provide a world to us - but if you have a Realm already this may be a viable option if you wish to do so.)

If the world is larger than 10MB you can upload the world to OneDrive or a similar file sharing site, and then share the link.

I am on a Nintendo Switch and can't upload a world. So any help from others having this issue would be much appreciated.

Here's a link to my world for Windows PC Bedrock World -197586509 v1.18.30.22 Beta created on 20220309:

https://mega.nz/file/aiATzIKT#1OyZAs0qH41owW-wLji_gtI9I-bnbSeQVxNCXA1rcic

I started this same Seed in the current version. Unlike the aforementioned world, the newly started world loads and plays correctly. I suspect old worlds are not converting correctly.

@unknown: This issue is about mobs despawning. Once they do that, they no longer exist in the world, so it wouldn't be possible for world upgrade logic to restore them. If that's what you expected, your expectation is flawed. If you mean something else, and it's relevant to this issue, please explain what you expected.

@Auldrick, Mobs, villagers and fenced animals all disappeared. When I leave the chunk or save and exit the mobs disappear in an existing world. The plains village x149 y72 z79 had villagers and animals in world v1.18.30.20 Beta. The villagers and fenced animals all disappeared from the village when I loaded the world v1.18.30.22 Beta. I restored the villagers and animals, and I saved and exited the world. When I reloaded the world, the villagers and animals disappeared. My expectation is the villagers and animals would be present when I reloaded the world. I created a new world with the same seed, v1.18.30.22 Beta. The villagers and animals do not disappear when I reload the world or leave the chunk where the village is located.  

The way the bug works is that entities are not being saved in the world when you quit. We already know this happens in 1.18.30.20 Beta. They didn't disappear when you loaded that world in 1.18.30.22 Beta because they were already lost when you saved in .20.

What you should do at this point to gather more information is to continue playing the world you created under .22. I would expect that, because it was independently created, it will still have the issue but that it will affect a different set of mobs, perhaps after saving and reloading several times. If that happens, your comment 3 above doesn't actually add anything new to the report because it's the result of a misunderstanding of how the bug works. On the other hand, if mobs no longer disappear in the new world, that might mean that the bug has spontaneously been fixed, which is unusual but which does happen sometimes. If you're no longer able to reproduce the bug in .22, that's additional information we very much need.