Bac0nAssassin

Tested it with the silverfish in carts and boats, no suffocation.

I've lost several parrots by leaving the nether and going to the overworld (those poor poor parrots). I'm the admin in my Realm and only my horse, donkey and cat have stayed in the world. Anyone else that has tamed an animal has lost it to a despawn. Our pens with sheep and pigs were lost to despawn, but the cows managed to stay? My villager breeder lost the breeders but the villager with the doors remained. The automated chicken cooker I made would lose all of the egg layers even though they're sealed in, come home to find a room full of chicken everywhere. I'm not sure if it has anything to do with how many zombies we spawn in at our zombie farm or not. Maybe I'll switch everyone to OP status like Joseph did.

I've experienced something similar to this in my Realm on the Xbox. I had a farm full of animals I bred, left the chunk and loaded up a zombie farm for XP, after some time (can't say how long), I noticed more and more animals disappearing, first pigs, then sheep, llamas and horses, but oddly enough not cows. Also found chickens escaping an automated chicken cooker, come home to a room full of chickens. My villager breeder lost all of the villagers it bred. I've resorted to curing zombie villagers and keeping them in boats for the time being.

I can get it to lag with just one named shulker box filled with named and non named items.

I can also confirm this problem still exists on Xbox One. The Guardian Farm we created in our Realm spawns no Guardians at all. I switched the game to Peaceful, logged in, logged out, switched it back to our normal difficulty and 1 Guardian fell through the trap. One.

I still experience this problem on Xbox One in my Realm.