mobs disappear

 I started playing only with version 1.11 (beta), and all this time I have encountered a bug: entities (mobs) periodically disappear: residents, trolleys, foxes on a leash. there is still a problem, and this makes it very difficult to play. I could not find any pattern in the disappearance: sometimes it is enough to leave the territory (unload chunks), and sometimes it happens after the world reboots (I left the game and stopped)