Named passive mobs randomly despawning in 1.17.40 Bedrock Realm.

I, as many others have, created a zoo in a survival realms world in bedrock 1.17.40. I have noticed that sometimes when I leave the chunks my zoo is located in and return, some of my named mobs have despawned, but not all of them. In addition, none of my unnamed mobs have despawned yet. I don't know if they are dying or despawning because I'm actually also experiencing a bug where mobs do not drop items or xp upon death 100% of the time. Thus, I haven't seen items as "evidence" of death, nor have I watched them suffocate or anything like that. The enclosures the mobs are in are also completely sealed so, for example, there's no way a wolf could hop in to kill a sheep and hop out. Can someone please help me figure out how to prevent this from happening again? I traveled thousands of blocks to lure some of these animals back to my base and I'm extremely disheartened that I have to do it again.