What I expected to happen was..:

the "hat" layer of the custom head to rotate a certain axis with the rest of the head.

What actually happened was...:
the hat layer decides to rotate on a completely different axis, making it look bad in any rotation except the head facing north on the ground.(it also looks even worse on the player)

Steps to Reproduce:
1. get yourself a player head /give @p player_head{SkullOwner:username}
2.wear it/place it to where it isn't facing north.