When you sleep in a bed with a block two blocks above, you can sink into the bed.
This only works in certain blocks listed below:
Lantern
Bell
Heads / Skulls (Player, Skeleton, Wither Skeleton, Creeper, Zombie, Dragon)
Grindstone
Hopper
Another bed (see MC-150447)
Linked issues
duplicates 1
Attachments
Comments 2
Forward-resolving to MC-162531.
In 1.14 I am experiencing this with beds as well (MC-150447).
I can also confirm that the problem exists for the other blocks reported above with the note that:
Hoppers only are a problem when they face a cardinal direction (facing downwards works fine).
Grindstones only are a problem when they are wall attached (ceiling attachment works fine).