The rifle which Robocop brings into the OCP theater at the end of the film is meant to be the Cobra Assault Cannon from the original film; however, not only is it a completely different gun from the first film, it is also devoid of any of the extraneous attachments and greeblies present in the original version.
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.
When Cain's men cut up Robocop, and when they discard his parts in front of the police station, we see his various parts moving. Normally that wouldn't happen since every part of him can't have an autonomous energy system.
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.
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.
In the scene directly after Officer Lewis hits Robocop with the board, there is a glimpse of her still holding it after she knocks Robocop off of the electrical box, yet in the scene directly after, she is holding nothing at all.
After Cain drives next to the telephone pole and knocks Robocop off the armored vehicle, Robo falls next to the pole with a solid "thunk." In the very next scene, Robocop is out in the middle of the street with no telephone pole near him.
When Robocop 2 extends a mechanical arm to Angie, from his point of view, she caresses it with her middle finger, then the shot switches to a side view where she is using her index finger, then the shot switches back to his POV and it goes back to her using her middle finger again.
When Robocop goes to the sludge plant to get Cain, his right hand gets shot off right at his wrist. Later, when they dump his parts in front of the police station, they throw out his right arm which is shown to be separated at the forearm.
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.)
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.
Robocop remarks how nice the Moon looks and Lewis replies that it's daytime. In fact the Moon can be seen during the daytime just as much as during the night, though it isn't as obvious due to the brightness of the sky.
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.
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.
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.
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 Robocop shoots the man in the head during the baby hostage scene, the fake baby's arm dangles limply by its cloth when it's almost dropped, revealing it to be a normal, store-bought children's baby doll.
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 Cain's henchwoman calls the mayor and he asks her to turn down the TV set and they do a close up of the phone she is on, you can clearly see there is no cord plugged in to it - and it's not a cordless phone.
After Robocop's right hand is blown off by the .30 caliber HMG, his "stump" is significantly longer than when it will be summarily amputated. Obviously his hand is only concealed by the long black Kevlar.
When Robocop is in the station after being dismantled he is hanging up by wires and tubes. His head is supposed to be human but you can see light from the back of his animatronic head through his mouth.