This does not seem to be similar. My issue was very specific to the enchanted elytras only going missing when dying in the nether by any means. everything else would not disappear. I first noticed it when killed by piglins and when returning, my elytra would be missing. Tested also in a new creative world by just standing on magma block, fire, and fall damage in the nether. each time I returned, the enchanted elytra would be the only thing missing.
Though I just tested this in version 1.16.0.60 and 1.16.0.61 and appears to be fixed when repeating the previous tests done in 1.16.0.59.
Not sure if this should be tracked separately, but item frames which had the items in them that disappeared can not be broken or new items placed in them also.
Gone through and repopulated my villagers through breeding, after about 15 of them, all hostile mobs stop spawning as long as the village farm is within my simulation distance and lag starts increasing, not nearly as bad in 1.16.0.51. To recreate, I just need to breed up a lot of villagers in the space of a simulation distance.
I'm now running version 1.16.0.58 that it is affecting, but also found it is affecting version 1.14.60 also the one just before that.
Same occurs on the latest beta 1.16.0.57 on an XBOX One X, Though occurs when you craft 64 at a time. It does not crash when making 63 or less at once in my testing.
Issue is resolved in the latest beta update, 1.16.0.53.
Seems to be glitched out villagers in my world after going from 1.14.30 to to the beta 1.16.0.51. I attempted to recreated it in a test world, but no success. So not specifically caused by them standing on a floating bed in a glass black. Untimely after several tests, it seems if I kill all my villagers it fixes the lag and mobs once again start spawning in the area. I've yet to repopulate back up to my 42 villagers to see if it's something specific with bread villagers compared to those from spawn eggs that I was using in the test world.
The bug is still present in beta 1.16.0.51 on Win 10 as well. attempted the several solutions suggested such as snowballs and others with no success in them laying their eggs.
Steps to reproduce:
1. Create glass wall, my example is light grey glass blocks
2. On realm or local saved world with default video settings, walk away from the glass wall.
Observed Results:
Glass wall turn gray and non-transparent around 4-8 chunks on realms and at 12-14 chunks on local saved games away from it.
Expected Results;
Glass will remain transparent up to render distance as is with Nintendo Switch and Windows 10 versions I've tested.