Something I've encountered in my Chosokabe campaign during sieges is when enemies man the walls there is sometimes a single surviving soldier from a destroyed unit who simply refuses to die to arrow fire. Not only were multiple groups of 94 accuracy Chosokabe Bow Samurai not able to hit these guys after several volleys, they would keep trying to exclusively shoot the supernatural dodger unless I manually switched them to a new target as the AI's other units moved in and out of my firing range.
This small issue adds too much needless micromanagement when using archer units against a fort. I started auto-resolving my battles because it seemed to appear at least once during every siege.