86's reflection momentarily disappears when one of his clones comes out of the cloning machine.
During the chase scene at the movie set back-lot, Sebastiani fires one shot, but two bullet holes appear in the set.
When Max and Larrabee are driving together, there is no window post ('B pillar') between the front and rear doors, yet the car used for the outside shots has one.
During the fight, Max has a gas mask over his face. When he takes off Norman's mask, his own disappears from his face between shots.
When Mr. Seigle is being pushed in to the emergency room, the stretcher hits a series of doors. Right after passing the elevators the camera goes in closer to Mr. Seigle and the door on the left has a broken window, but when the camera pulls back, the window is unbroken. It is the next set of doors that has the broken window.
In the clone fight scene, the face of Max's stunt double is clearly seen in several shots.
During the sequence where Agent 86 and The Chief visit Carruthers at the apartment, the viewer can see in some shots that Don Adams is wearing a hearing aid in his left ear.
There are multiple times in the cloning sequence where the reflection of one clone in the mirror behind the clone machine vanishes as another clone emerges. The set designer must of not have been aware of the many split screen shots needed for the scene and how a mirror would be a problem in those scenes. Also when a group of clones emerge one by one, close together, there are times when they breech the one of the split screen lines, making part of them disappear.
In the chase scene where Max is driving his desk, chasing the chief, the chief's car goes up on two wheels to get past the parked Pinto. As the Chief's car passes the Pinto, the ramp that forces the car up on two wheels can be clearly seen.