Revealing mistake: During the fight scene between Han and Bruce Lee toward the end of the movie, Bruce Lee knocks Han to the ground. The shot changes to show a frontal view of Bruce as he lands a crushing kick on Han. It looks like Han was replaced with a dummy for this shot, as Bruce's kick seems to just send Han across the room. As I reviewed the scene, I could see that Han was actually a dummy of some sort .
Revealing mistake: In Han's first scene, when he enters the banquet hall to welcome fighters he holds both arms out and the fingers on his solid metal hand are spread. Later on after beating Williams to death he takes off his glove to reveal his metal hand. Look at the glove before he does this; he moves his fingers.
Revealing mistake: When Han's daughters/bodyguards are throwing daggers at the apples in the banquet room, one girl just blows the dagger out of her palm and catches the apple in mid air impressively. However a keen eye can see the wire attached to the dagger that pulls it from her hand (slow-mo is not necessary).
Revealing mistake: When Lee's sister is seen running from the men pursuing her, she falls down and you can see the stunt mat she falls on. It looks like the makers tried to cover it up with some dirt but if you look at the lower left corner you can see the green fabric of the mattress where they missed a spot.