While using it in the right hand seems to work fine, using it in the left hand seems to highlight multiple problems:

• The right hand immediately snaps to the player's side as if they were standing.
• The left hand appears to be completely stiff and doesn't use the expected aiming animation.

Bows and crossbows appear to problems when crawling as well, as the left hand and right hand use animations also differ.

This seems to be a left-hand exclusive issue. In addition, it seems as though having the left hand as the main hand results in the trident aiming animation that happens when the right hand is the main hand not playing.

I can reproduce all of that in Vanilla mc? When aiming the arms won't move, the other hand will snap to the side, the trident is held the wrong way around.

Did some more tinkering, I think this should behave now like vanilla, maybe a small fix here and there. Tridents for example will still be upside down, crossbows not use an aim animation and bow animations be somewhat weird.