Tamed, cured, or otherwise trapped mobs despawning

We are currently on a realm with about 7 people, about only 2-4 are active at a time. We've been experiencing issues with our cured/tamed mobs. They have inexplicably been disappearing. We will log on to a villager missing from our trading post (all villagers are secured by walls, nothing gets in or out) and it only happens randomly. There are no mobs in or around the area that could harm and kill our cured villagers, and it will only be one random villager that just despawns. We have done some experimenting and have come to no conclusive data other than this being a bug. We've had some mobs cured/tamed that are named with name tags and some without and we've had both disappear. We've had horses tamed that are tied to the same post as other horses and two will randomly despawn. There is no way for them to die, they are despawning. Please look into this issue as it is causing our group to become increasingly frustrated and it is preventing us from advancing in the game. Thank you for your time.