Near the beginning of the film as Harry enters Cini's apartment we hear a gun being cocked and then see a .45 pistol being pointed at Harry's head. You can clearly see the hammer is not in the cocked position.
In the final scene when Alan starts the E-type Jaguar he does it by turning the key, yet that car (as to all pre-1968 XKEs) starts with a starter button on the dashboard, as was demonstrated when it first appears in Harry Mitchell's garage.
When Mitch is taken to a secret location to meet with the extortionists, he sits in a wooden chair against a "wall". He sees his mistress shot five times. After the bad guys leave, he jumps up when he realizes he is in the chair she was murdered in. But, when he first walks in, there is no blood on the chair or wall behind him.