Revealing mistake: When Kikuchiyo tricks and kills the gunner, he chases him a short way, then stabs him with a sword. Even though there's a tree blocking the action, you can still see he never actually stabs him, he just lightly stabs the ground near him.
Revealing mistake: At the last battle Katsushiro stabs a bandit who's climbing the fence to escape. It's completely obvious that the sword never penetrates the bandit. In fact, Katsushiro just seems to just tap him with the tip and his clothes aren't even torn from it, yet he still dies. Maybe a heart attack?