Mobs like villagers and/or sheep looks like they or float of into another direction or back from somewhere and the villagers mainly do that when sleeping in their beds when I get back there is only two left then log out and back in again then all of them are back. A lot of times while building and catching something in the distance it is like it teleports from faraway into its place it is meant to be. only started once the update came along of 1.16.100. 

Also if the villagers don't float away they sleep sideways in their beds or they freeze in a single spot and don't do anything and take up a completely different hit box.