The bug
Occasionally, tile ticks are not removed successfully from the save file, causing them to linger there eternally. This in turn causes the affected blocks to no longer be able to get ticked.
This is known to affect the following blocks:
Repeaters
Observers
Comparators
Daylight sensors(?)
... so probably all blocks that can receive tile ticks.
When the TileTick values of the affected chunk are purged via a third-party tool, the affected blocks start working again.
To reproduce
As of right now, it is unknown what causes this issue. There are some worlds however in which this issue occurred.
https://drive.google.com/open?id=1j0nac0qWlOkMg-DFuhjRgrLlUk_upBJk (from this ticket)
https://mega.nz/#!gFplBCbL!OLzdTb0sMM2KA9_PS_hrHhE7D9I06bOYuM7m7B8EP1M (from MC-158935)
Original description
I've set up a few flying machines using sticky pistons, observers, and slime blocks for a witch hut farm. It worked for a while, but now suddenly the back observers in all 3 flying machines have ceased to work. This is after an overnight AFK session at the farm. I've attached pictures of one of the observers, without the flying machine. The observer are connected to a redstone line for ease of demonstration of the bug. No matter how I update the observer, the observer will never fire, and the redstone line will never turn on. The observers are all facing the correct direction, and this bug only happens at one certain block location in each flying machine platform. All observers in other positions work fine, it's just these three specific positions that seem to be causing the observers to not fire. No other redstone signal is making its way to the observer.
In addition, I've downloaded the same world that the server is running, and the issue still persists in single player. The issue also persists after restarting the server, and still persists after re-uploading the world to the server. Optimizing the world also does not fix the issue
Related issues
is duplicated by
Attachments
Comments
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violine1101
Please attach the zipped world file here. If the file size is too large, please upload it somewhere else and link to it here.
Also, have the chunks that the witch farm is in been reloaded while it was running? Some redstone contraptions, especially those with slime blocks, break upon reloading. I don't know if that's the case for this one.
migrated
Here's a google drive link to the zipped world folder: https://drive.google.com/open?id=1j0nac0qWlOkMg-DFuhjRgrLlUk_upBJk
I've torn apart the flying machines themselves to highlight the actual issue: the observers marked with polished granite don't fire when supplied with block updates.
The chunks of the witch farm were reloaded, and I've experienced that kind of breakage many times before. In that case, simply rebuilding the flying machines has fixed the problem. This breakage seems very different though, as now even without a flying machine, these observers cease to work.
violine1101
Thanks. Can confirm.
migrated
I know why the observers aren't firing, and I know how to fix it, but I don't know what causes the bug in the first place. I've been trying to recreate the cause of this for a while but haven't been able to figure it out. I've had it happen to me with torches and repeaters.
If you use NBT explorer to open the region file (r.-1.-2.mca in this case), and go to the chunk with the observers (-32,-43), you can see a bunch of entries in the Level>TileTicks section. Most of these are oak leaves, but there are a few that are observers. Deleting these entries from the region file will make those observers work again.
That was pretty much what I expected, but what I wasn't expecting was for some of the observers to still not work. Turns out that some of the observers tileticks are in the section for the neighboring chunk (-32,-42), instead of the chunk they are in. Deleting all the tileticks from both chunks made all the observers work again. This makes me think that maybe the game sometimes tries to add/remove the tiletick entries to the wrong chunk, and that's why they aren't being cleared out correctly.
Someone I was talking to thought that the issue happened to them when they died, and the two times I had it, I noticed it after I died as well. Not enough for me to say it's a direct cause, but it's a possible link. I haven't been able to find a way to cause the bug yet. I'd be interested to know if this happened immediately after you died as well.
migrated
Thanks for all the info! Deleting the entries from the chunk did fix the problem.
The issue did happen to my when I died, however I dismissed it because I was killed by a player who stayed in the area and loaded the chunks for a while before and after I died. This other player also confirmed that the flying machines were all working properly after killing me, before logging off the server. Perhaps it's an issue with chunks in the vicinity of a dead player who has yet to respawn? I'm trying to replicate now it in single player and multi player by staying on the death screen for a while after dying near various redstone circuits and tile entities across different chunk border configurations, but even after many rounds of waiting with high tick speeds, I have yet to replicate it.
violine1101
Very similar issue with repeaters in this ticket: MC-158935. Probably caused by the same bug.
violine1101
Question to everyone experiencing this issue: Was the affected world ever opened in a snapshot? MC-140985 suggests that this was an issue during the 1.14 development phase that got fixed in time for the release. Worlds opened in one of these snapshots would be affected.
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The first time I got the issue was in a world that was started in 14.3-pre1.
violine1101
Alright, then that theory is debunked.
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My issue was in a world that started in 1.14.4.
RedCMD
Can confirm bug in 1.14.4 when disconnecting from a server, while the comparator was updating
When looking at the region file, I see the tileTick time for the observers were at a extremely high number
It must be when a tileTick is getting unloaded while its at 0ticks left, it must -1 off twice and underflow into the negatives (and because the variable isn't signed, it goes to max 2^31)
-1 before saving, then -1 again after loading maybe?
Somehow all my dead comps fixed themselves
migrated
This is still a problem in 1.15.2. It happened in my 1.15.2 multiplayer world.
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I managed to replicate this bug in 1.15.2 in a multiplayer world. Doesn't change no matter what, relogging doesn't help either.
migrated
Can confirm it is possible in 1.15.2 I had it happen to 2 blocks with repeaters on them and nothing fixed those blocks
migrated
Hello, i've come upon this bug in 1.15.1, I need to say tho, i'm on spigot server, not entirely vanilla, but the problem seems to be the same, it's 2 repeaters and an observer the ones that i'm having an issue with, and only in those coordinates; redstone outise of those coordinates seems to work just fine.
migrated
Version: 1.16.4
I have attached a region file from our server that has been running for almost 6 years. In at least one region file there are observers and repeaters with totally incorrect time values and removing and replacing the blocks doesn't reset the time values.
The problem was also covered in a video: link Funny repeater bug
(Please note that the attached region file is slightly modified compared to the one in the video.)
NBTExplorer showing the problem when a broken observer is replaced by a repeater:
[media]
Panda4994
Is anyone still experiencing this issue in the current version?