When Gary is stopped at Diane's apartment by the secret service, the agent speaking is wearing a brown blazer. After Gary says, "Who's she got in there?" we cut back to the agent and his blazer is now dark blue.
When Paul steals the yellow sports car after leaving the police station, he takes off and there's a shot of the tachometer over his shoulder. The tach revs up close to red-line, but the engine sound doesn't match.
Paul is handcuffed to a wooden chair in the police station. After the mob chasing Marisa goes through the police station leaving Paul alone, he goes out to the street where he breaks apart the chair leaving the handcuffs still visible on his wrist. He takes an abandoned car to return to Diane's wedding where he gets out of the car and the handcuffs are gone.