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.
Revealing mistake: When Matrix reaches Arius' mansion (in actuality the Harold Lloyd Estate), he is rushed at by several soldiers of Arius' private army and starts shooting at them with his RPK. In one shot from Matrix's rear we can see him shooting four soldiers at the same time. However, the two soldiers on the far left drop dead even though Matrix is aiming his weapon to the right.