Revealing mistake: In the closing scenes where Robocop pulls up outside the offices of OCP, he fires the rifle (in fact built around a slightly modified Barret Light 50 fifty caliber semi-auto rifle) at the ED209 across the roof of the car and destroys it. As he watches the robot and grins just before putting the rifle down, you can see he has what is known as a "stovepipe", in other words the last fifty caliber blank crimped shell fired has failed to eject fully and is stuck there poking out the side of the action just in front of his face (towards the left of the picture). The crimped end of the large brass case is easily seen. This is common with blanks in a gas operated semi auto which may not cycle the action fully - not the live ammo he's clearly meant to be using.
Factual error: The film takes place in Detroit, but it is glaringly obvious that it was shot in Dallas. First of all, in the early scene where Murphy chases Boddicker's gang on the highway, Reunion Tower, one of Dallas's most famous landmarks, is visible in the background. Much of Dallas's skyline is also visible in the final scene where Robocop confronts Dick Jones in the OCP boardroom. (00:15:15)
Continuity mistake: When Clarence is in Bob's house killing him, he sets a grenade on the table. If you watch carefully after Clarence pulls the pin out of the grenade, the timer is actually facing towards Bob as it is set on the table. When Bob crawls over to it the numbers are facing towards the camera, so we can see it counting down. (00:58:33)
Revealing mistake: When RoboCop is getting into his car after remembering about his former life, and breaking out of the police station, look at the bottom of the screen. You can see that Peter Weller is only wearing half of the RoboCop costume, his right leg comes into shot as he gets into the car. (00:46:40)
Continuity mistake: When the guy holding the mayor hostage gets thrown out of the window, we see the only two TV cameras near the location follow his fall down to the ground. A few seconds later on the news though, the footage is the same shot we saw in the film, staying focused on the window. (00:39:55)
Plot hole: When Murphy is in the changeroom at the station, he learns that an officer has just died and that his funeral (according to the captain) would be the next day. There's simply no way a funeral can take place one day after someone's death. All the planning, prep work and getting the body released to the funeral home would take about a week...plus many other things. Simply cannot be done.
Continuity mistake: You have to watch REALLY closely for this one. When Clarence and the gang are in the mill looking for RoboCop, we see RoboCop on the floor above them. He walks to the ledge with the mirror in his hands, but when we see a closeup of him, he has to bend down to pick up the mirror. (01:24:37)
Continuity mistake: In the end scene Robocop shoots Dick Jones out the window while he is standing in front of the television screens, then he spins his gun and puts it into his right leg. The camera view changes to focus on his leg, and you can see he is not standing in front of the screen and a person's legs appear standing behind Robocop, with black corporate pants and leather shoes. In the next shot when it focuses back on Robocop, he is back in front of the television screens again after putting his gun away. Obviously the leg view is from a dummy, because the blood & damage on it was missing in that shot. (01:36:00)
Visible crew/equipment: Just before Clarence Boddicker crashes his SUX into the water, the camera view zooms down to the driver's window. If you look in the paintwork below the drivers window, you can see the camera and operator being reflected. (01:29:35)
Continuity mistake: RoboCop walks past the police department lobby for the first time, following Bob Morton. Robo is walking at a very slow, deliberate pace. The rest of the cops in the department run as fast as they can to the far end of the building to see where they are taking him. Despite running about four times faster than Robocop he has already cleared the end of the hallway and is in the regeneration room before the cops get there. (00:29:50)
Revealing mistake: When Robocop uses his thermal vision to see the hostages and gunman through the wall, you can see a long zipper in the back of all the thermal color pattern costumes they all wore to simulate thermography. This was most likely invisible to the eye in a dark theater but on an HD screen, it shows.