I was testing my player head animation, and I pasted a player head of my current model and it seems to not animate in the third person. It animates fine in first person.

No real clue why.

EDIT: There is a second issue found, if the player head is animated (or if there is a player head of your model at all IDK), and if it's in your inventory and/or placed, gestures and poses stop working. If the player head is destroyed and does not exist in the server (or exist in a unloaded chunk, IDK) or in your inventory, the problem is rectified, but not fixed as the poses and gestures will break again if a player head of your model appears again.