Since the previous Nether update, I and my other realm users have noticed unusual behaviour for despawning and respawning, mainly despawning. Usually, it's mobs despawning either extremely quickly or mobs such as Horses and Villagers (even with nametags and tied) vanishing. Respawning seems a little odd, I've noticed mobs spawning in well lit areas but I'm not sure if I'm just imagining that one, to be honest, but I've noted several incidents of these despawns from my realm's users.

I don't particularly have an idea as to what circumstances causes the despawning, it just seems to happen at random. But before the update we never had this sort of behaviour, rarely it would happen and we would shrug it off as a small error, but we have had this new world for about a month and many mobs have vanished without much reason.