maybe try checking if your drivers are up to date n your windows as well
my friend also has the same problem as me, and people from the minecraft discord have been dealing with this same problem .
not sure if this bug has reappeared or if its part of a different issue.
sometimes a furnace will give xp after a box of smeltable items go through it, but occasionally no xp will be given, even tho its the same furnace and the same amount of items went through. Breaking and replacing the furnace seemed to help but haven't been able to recreate it since. (happened playing xbox one, using realms. others have also mentioned this happening to them, but I don't know the devices they use)
confirmed for 1.16.1 still an issue.
for anyone who ends up in a slime chunk and spends alot of time in the area, the game can have problems loading the nether when you do finally go through. If killed when going through the slimes do despawn. This is a big problem for realms or servers that have a community area within a slime chunk and prefer both portals to be low down in the world for better linking and easier nether tunnelling
I've had this happen countless times, using bottom half slabs and carpets. always seems to be the big slimes, and they are often unable to move due to being partly inside the block. there is also a very similar bug that can be recreated by going to a slime chunk and digging out a 2 block high area close to the bottom of the world, you will get big slimes spawning partly inside a full block in the same way you get them spawn inside half slabs.
nothing is working, all of my drivers are up to date as well as my firmware, soft/hardware, and i also disabled vsync because people said that would help but it didnt work for me .