If a player on a server sleeps in a bed placed next to solid blocks, when they wake up they will often take a point of suffocation damage, as though they were temporarily placed inside the solid blocks.

The player does not visually appear inside the solid block, but is instead placed on a valid clear block.

This is very noticeable if you have placed a bed in the corner of a room, as you are likely to take damage from the walls of the room, even though you are placed on the clear side of the bed.