Keep an eye on an early scene when Mona Clyde places a note under the shop door to the Priceless Antiques shop. It appeared that she placed it entirely under the door, but when Tracy comes by to retrieve it, a large portion of the note is visible before it's picked up on the other side.
In the final chase scene, just after Cueball gets out of the taxi, there's a shot of Tracy's car coming around a corner. The shot is flipped; a sign on a building is clearly backwards. The ensuing scene in the freight yard is a confusing mix of day and night photography.