Friendly / unfriendly mobs dying for no good reason

I had a nametagged zombie die multiple times. The zombie was used in a villager trading hall. It was in a secure spot and nametagged and surround so it couldn't interact with any other mobs. When I returned to my trading hall 3 times all that was left was zombie flesh and a block it was holding floating on the ground. It was in an enclosure with a 5 block high roof. I made the roof 4 blocks high and it has since stopped dying.

However, after another 2 hours of gameplay. I went underground away from my villager breeder. Inside the breeder containment area was approximately 10 villagers, 5 adult villagers and 3 baby villagers as well as 2 baby villagers in minecarts. I went underground to mine obsidian for about 10 minutes and returned to the surface and all of the villagers in the breeder are gone.

This never happened in earlier version.