An Asian woman in Cain's limo pleads for her life during the Nuke factory bust at the beginning of the film. When Cain shoots her and throws her from his car, a Caucasian woman in different clothing is seen falling out of the door in a subsequent shot.
Robocop apparently weighs several hundred pounds, as demonstrated when seven officers struggled trying to lift him after he grabbed the high voltage contacts, yet Robocop's weight never seems to be a factor when using various vehicles, i.e. police squad cars or the Harley-Davidson he commandeers to catch Cain.
At the film's finale, it is impossible for Robo to reach the hole on the street to climb out, as there were no mountable structures near the damage.
When Robocop throws the treacherous cop against the Midnight Resistance arcade game, the machine falls over. A little while later it's standing up again.
When Lewis knocks Robo away from the equipment he's electrocuting himself on, there isn't enough clearance for her to actually swing the board. Additionally, the position and length of the board changes significantly between shots.
The telethon fund-raising goal to get Detroit out of debt is 37 million. This is a ridiculously low figure for a city the size of Detroit, even in the state of decline depicted in the film. At the time the movie was made, the annual budget for city of Detroit was more than one billion, and could run 50 million budget deficit in just one year. When the city filed for bankruptcy in 2013, it was in debt in excess of 18 billion. There is also the issue that failure to pay the debt would apparently cause OCP to gain control of virtually all of the city's public services. The combined worth of that would likely be in the billions, and as such having that as collateral for a 37 million dollar debt makes no sense.
Cain's disembodied brain is still connected to his spinal column which, which all his nerves and vertebrae, is much bigger than the hole at the base of his skull. Despite his head being severed, and its cranium removed, Cain's skull shows no other signs of the damage that should have been necessary to remove his spine.
In all of the shootouts that Robocop 2 is involved in, he fires many more rounds than he is capable of carrying in his mini gun. This is an especially glaring error in the final battle, when he shoots several thousand rounds without reloading his mini gun.
When RoboCop ripped Cain's brain module out with its wires and thrown down onto the street with him, his RoboCop 2 machine body should have shut down immediately, but the machine still stood active until RoboCop completely smashed the brain.
The tazer used to incapacitate Robocop is designed to transfer amperage safely in regards to the shooter. There is nothing Robocop can do to it to make the amperage return to the shooter.
Robocop was easily picked up by the electromagnet but his armor, which is supposed to be made of titanium, would be only very weakly magnetic.
When the little league team is robbing the electronics store, the team's coach is shooting at Lewis. During the shoot-out, his baseball cap slips off and you can see the bullet wound on his forehead moments before Lewis is supposed to shoot him there.
When the surgeons harvest Cain's brain, it takes very little time and appears only to involve the brain. Later, the jar specimen shows a brain and complete spinal cord, which would take much longer and would be much more difficult.
When the Mayor's limo arrives at the abandoned industrial site for the meeting, it is an early 1990s Cadillac. Later, when Robocop passes the limo - which was destroyed by Robocop 2 - it has become an early 1970s Cadillac.
None of the Nuke addicts, who shoot Nuke into their necks on a regular basis, have any needle track marks on their necks.
In the scene where Robo is lifted up via a car magnet, you can see the wire that is attaching Peter Weller to the prop "magnet." It's on his side, near his hip.
When Robocop 2 extends his arm to hit Robocop, it is obvious that the extension is a forced perspective trick as the arm becomes at least four times longer to get out of frame. Robocop is subsequently knocked into a wall that previously did not exist, as Robo was standing in front of an open hall.
When the 3 robbers rob the gun shop Nick the gun shop owner is behind a til yet its in the middle of the night and the shutters are closed there would be no reason for him to be behind the til.
Right after Robocop breaks the chain on the outside fence and returns to the car to drive into the abandoned factory where Cain is hiding, a cable can be seen attached to the rear of the car right before it explodes. (The cable was most likely used to trigger the explosion in the empty car as it moved forward.)
Reflected in Robocop's helmet when Dr. Faxx is trying to reprogram Robocop.
During the shootout between Cain's gang and the Detroit police, one police officer falls down a flight of stairs. Just as he falls down the final stair, a hand comes out to break his fall.
The phone number on the sign outside of the River Rouge Sludge Plant (Cain's hideout) has a 312 area code (Chicago), instead of a 313 area code for Detroit, which is where the story takes place, and the city of Houston can be seen in the background.
When the corrupt cop Duffy gets eviscerated alive by Cain's "surgeon", he cuts trough cloth instead cutting directly through the skin on his chest. This makes no sense, unless it was done during production to avoid problems with the rating of the movie.
Gilette (George Cheung) and Catzo (Michael Medeiros), two of Cain's henchmen, are last seen as soon as the police raid on the sludge plant begins, then disappear. It is unknown what happened to them.
The doctors who harvest Cain's body parts save his brain, his entire spinal cord, and his eyes. In the final model of the Robocop 2 unit, it appears only the brain and a small section of the spinal cord are used. Also, the actual brain used in the unit appears to be much smaller and shaped differently than the original.
A Robocop would never been required in every city in the United States, not just in Old Detroit.
When Robocop watches his wife's house, the boom mic's shadow is clearly seen on top of the windshield.
When Cain is loaded into the ambulance, he is loaded feet first, instead of head first.