If your bed is on the ground, you will just fall off the bed once, but if it's in the air, You will fall REPEATADLY. You will aproxximately fall over the bed in the air every Minecraft tick.

How to reproduce the bug :
1. Place a bed
2. place a block on the upper part of the bed
3. make sure it's night
4. Sleep on the bed
5. you will slip down the bed

What I expected to happen
I expected I would sleep normally on the bed.
And i slipped down.