Steps to reproduce this bug
-place down a bed 
-stand to the side of the bottom block of the bed
-walk over the bed to the other side of the bed while holding the right click
-repeat until the bug happens

When you follow these steps you will take damage with no clear reason.
You shouldn't take damage while doing this.
 
This bug I found only happens in realms
It's only a half-heart so it's just annoying

this bug also happens elsewhere such as doors but this is the easiest way I've found to reproduce it.

In the video is me following the steps provided above