Pär-Erik Segolsson

No, I have not experienced this in 1.18 or 1.18.1 it went away during the snapshots, can't remember which version though. 

ok, found the culprit. it was a datapack. so NOT a game bug! it was a datapack bug. so can any mod close this one?

ok i've done some basic testing and when i removed the 3 armor stands i had in the world(two at spawn and one in my base the loading of the world was much much smoother. so i guess armor stands as an entity is the reason i get massive lag spikes when loading the world. it shouldn't be this bad though with just 3 off them. 

edit: ok so removing the armor stands worked when i had the game running but when i restarted the game the issue returned, the first loading of the world after restart is horrible. 5-15fps for almost a minute before it stabilize and i have the normal 50-70 fps.

yes, if i remove all resource packs and datapacks it still does this. 

Here is the world that i made the video in: https://drive.google.com/file/d/1vt_TafzDqCudC6uVvn0M7xW3uqqdDYAG/view?usp=sharing 

however this happens in all worlds after pre4, didn't have this issue in pre3 or earlier.

also if you look in the video how the Memory usage behaves, i think there might be something fishy going on. i've never seen it go past 4gb but for the most part its just running from 0 up to 3999 and then resets and keeps doing that over and over.

after some more testing this morning i think i've found the problem. hoglins on top slabs don't seam to pathfind correctly, the don't seam to see the drop shute as their way off escape if the floor is made of top slabs.

When i replaced the floor with full blocks they started to behave as they should, its wierd that this only happen in a world that i have upgraded to 1.16 though. as i built the same design in my 1.16 test world and there it worked fine using top slabs.

oh sorry about the version hickup, but think it was the only one i could choose when i wrote the report. anyway added a short video showing the bug, recorded on my realm world, same thing happens in single player where i have removed all datapacks and run pure vanilla.

oh sorry about the remaining items, thought i had cleared them all before i uploaded. in 1.15.2 everytime i made a furnace array using hoppers in that general layout i had losses and still do in 1.15.2!

But in the new 1.16 i don't have this problem anymore . upgraded the same world i uploaded and have tried it in a brand new world as well without issues so i guess you could mark it as resolved. unless you guys still fix things in old versions? 

i did add a world download in an earlier comment(02/jun), not the same as the world in the video but the same dropper setup is available in that world.

made a quick video here showing how the droppers are setup: https://youtu.be/re6LZPTaWzc in this test i ran 27 stacks of sand thru my furnace array the result of the run at 4.30 into the video.

(and no, no items getting stuck in the furnaces)

you might lose as little as a few items or as much as 9 stacks, seemingly random from time to time.

This is in 15.2. have done a few tests in rc1 and have not had any losses there yet so something seams to have changed in rc1 from pre7.

this also happens if you run the items thru droppers, if you "spit" out enough items at one time some of them simply disappears so its not just player related the game simply can't keep up with the amount of items and just ignores(delete) the items it can't handle. so if you have say a furnace array with 32 or more furnaces and use droppers to send the items thru a water stream to the player or a chest and you smelt 27 stacks you might in worst case scenario only get 14 stacks back. 

i also did link to other bug reports in an comment but it seams to have been removed...

This also happens in the latest snapshot 20w22a

Well not sure what that will help, because the bug is in all the worlds i create so it is a game bug not a world specific bug, but here is the server world that i use: https://drive.google.com/file/d/1tY1Mk863rCvU9X2QvqJirqnGvDSPpKeQ/view?usp=sharing 

The furnace array is located at -2531 19 1676 (to test it grab 27 stacks of sand or stone from the chest and drop it on the red sandstone slab by using ctrl+q (or put it in a chest/shulkerbox on top of the red sandstone slab) smelted items will come up thru the trapdoor in the floor so stand on it and wait.

i never get the 27 stacks back. running with 5 stacks at the time might get you 5 stacks back. but the more stacks you use the bigger the loss. i think it has to do with how the game handles large amount of items, it seams to freak out and simply delete some if there are to many for it to handle.

Hosting it myself. Vanilla server, so no mods. The bug is present in both singleplayer and multi-player. 

added a crash report, i think this might be related to the bug where if you ctrl+q items out of your inventory some of them disappears.(MC-116618) seams very similar as about the same amount of blocks/stacks vanish. if any mods/devs wants to check this one out i can boot up a server, just let me know, and provide playername so i can whitelist.

Seams like it is fixed, ran a 2 hour test and have not seen a dolphin spawn in bubble column in 15.1. 

world download, empty cept for the farm: https://drive.google.com/open?id=1iWDF7TH0h15srrN_r61Thj3FpSclQBz0

as soon as the water was placed the lag spikes began

made some adjustment to my ironfarm and removed the water ontop of the platform(slabs) and now its silky smooth again, looks like there is an issue with the water mechanics. but i cant be sure i'm no gamedesigner. but if it barks like a dog it most likely is a dog right? 

It doesn't happen in 1.14.2