I'm the last 2 realms I have made with my friends my cured villagers are disappearing very regularly. These will be villagers that have access to beds, a work station, have been traded with multiple times, have named tags and the area is extremely well lit and they are in buildings that cannot be accessed by any zombies to kill them. This even happens on hard mode so if it were zombies they would be infected not killed. It cannot be pillagers spawning or somehow getting in because then all my villagers would have been killed not just a few at a time. Even putting some iron golems down there makes no difference.