When you duel wield tridents, 1 of them should activate, like in 1p_duel.png. However, in 3p_duel.png, both arms are held. You can also notice that the trident in the offhand is backwards.
When you sneak, the animation becomes wierder. The tridents hover above the player.
The swimming animation is also affected by this glitch.. You can clearly see the trident and even other items not touching the player's hands.