Visible crew/equipment: Just before he shoots the first thug, when he realises he's being followed, the camera keeps cutting between the characters, and when it cuts to Bronson you can see the shadow of someone walking along to his left. But he's supposed to be alone. (00:43:15)
Factual error: When the cops are staking out Charles Bronson's apartment, one orders the other to go to a pay phone and call him. He runs towards Riverside Drive, going west, and finds a broken phone. Then he runs to a subway station and makes the call. He returns from the same direction. Well, there are no subway stations on Riverside. The nearest is two long city blocks away, going east. Even if he ran that far, he would not have returned from the same direction - he would have come from the east.