One day I found a bat in my room, so I nicknamed him so that he doesn't despawn.

When I return from My mining session, I found that the bat was sleeping with a one block gap from the roof. Normally he would be attached to roof.

Observed Behavior:
Bat sleeping with One block space from roof.

Expected Behaviour:
Bat sleeping with being attached to roof.

Though this bug is of low priority, but a bug is a bug.
Also it would be good if there was some way to leash the bat  ; )