Revealing mistake: After the one bad guy crashes into the giant vat of Toxic Waste, hardly any of the liquid from the container spills out for the first two shots. Then a few cuts later, almost all of it pours from the back of the truck. Judging by the size of the hole it left, more liquid should have been coming out around the truck, not just through it. (01:29:00)
Revealing mistake: In the firing range scene, before Officer Lewis puts her gun down, and leans forward to look at Robocop shooting, we see him fire three shots. Look closely the second time he pulls the trigger. He pulls the trigger, but there is no ammo sound, nor is there a firing spark. This is in the VHS version. (00:32:10)
Revealing mistake: When they're supposedly tightening down the L.E.D. the scientist is using a normal drill bit attachment. (00:27:00)
Revealing mistake: As Emil is being washed out from the back of the truck by the toxic waste, it's obviously a stuntman. The stuntman appears to have a dark mohawk which does not match the actor's hair.
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.
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)
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.