On the latest Minecraft bedrock update, every time I log in and out of my Minecraft world the mobs in my simulation distance de spawn, including passive mobs and pets. My dogs, cats and my 4 natural pink sheep's de spawned. It doesn't matter if they have name tags or not three of my had name tags and they still disappeared.  I doubt you can do anything to help me right now, but I hope you can address the bug so it doesn't happen to anyone else.