Broken hand.

Whenever I sit on something and then go to 3rd-person and back or go to inventory and out, my hand gets broken.

Steps to reproduce:
1) Sit on something (Minecart, Boat, etc.)
2) Go into 3rd-person or go into Inventory.
3) Get out of Inventory or go to 1st-person.
4) Whimper in pain.