It seems that the heads of the piglins stays off centered after performing their celebratory dance. A temporary fix for this is to restart the game, not rejoining the world, only restarting the game.
piglins heads are not in the right position
Bug with helmets on Piglins' heads
Piglins have a dislocated head.
Piglin's Golden Helmet float beside it's head.
"Hat" layer on helmets detaches from Piglins' heads while bartering