Revealing mistake: During the stunt where the police van flips over (as a result of the rocket launcher attack) you can see the telegraph pole section used to flip the van over. It rolls down the road. (Stunts involving flips rely on a mini pile driver under the vehicle, as opposed to using an explosive charge by itself which can be too unpredictable).
Revealing mistake: At the end of the fight between Matrix and Bennett, Matrix throws a pipe through his body into the steam duct behind him. However, immediately after he is pierced by the pipe, we see Bennett slide about half a foot down the wall, which would be impossible with the pipe lodged in behind him.
Revealing mistake: The scene with the shack has many mistakes, but only if you play it in slow-mo. First, he throws the circular saw at the guy in the window, the saw is moving on wires and he has a hairpiece someone just pulls off with a wire. The next guy he stabs with a pitchfork, and Arnie just lightly stabs him and the guy falls forward holding onto the pitchfork to make it look as though he was stabbed. Arnie then throws a saw at a guy hitting him in the chest. The guy actually just catches the saw in his arms in a way to make you think he got hit. Then Arnie swings some sort of gardening tool into the genitles of a man, but he actually stops it before it hits the guy and the thug just holds onto the handle. Finally, Arnie hacks off the forearm of a another man. You can tell that his arm was fake from the elbow on.