Risky Business (1983)

Revealing mistake: When Joel rides his bicycle to the train station, the film is reversed. The numbers on the train that goes by are backwards.

Revealing mistake: When Joel's parents are talking directly into the camera just before they leave on holidays his father takes him into the room with the equalizer. It is easy to see that when the music is playing the equalizer is in fact off. This is proven when the father pushes the button and the red light goes on.

Revealing mistake: When the Porsche comes to a stop at the end of the boardwalk it is stopped by something that causes it to jerk backwards then roll forward slightly such as a chain or rope. It is moving too fast to stop on its own and couldn't be from a loose board because it rocks freely.