Each time a player tries to reload a crossbow in first person the animation doesn't play except for the first time. This is hardly noticeable since the animation still plays in third person and in the hotbar, but paying close attention reveals that the item itself doesn't change its texture.

As stated before, this is hardly noticeable due to the item being angled in such a way that the player won't notice at first but this can really break any custom made resourcepack that uses custom animations for the crossbow.