1. When there are 2 beds right next to each other and villagers sleep in those beds half the time they go farther away from each other and (I'm not sure but I think there has to be a wall behind the beds and sideways)
eventually, they go into the wall and become invisible. You can see that there are invisible by spawning a zombie. (i don't have a picture)
2. When a villager sleeps in his bed sometimes he actually isn't on the bed (Picture below)