Plot hole: Necros had absolutely no way of knowing that Bond and Saunders had arranged to meet at the cafe when they did, and wouldn't have had anywhere near enough time to track them down and set up his elaborate booby trap. Saunders only suggested the meeting place and time a few hours earlier, and it was kept strictly between him and Bond. The scene in Tangier where Whittaker tells Necros to kill another British agent takes place on the same day Bond arrived in Vienna; meaning that Necros got from Tangier to Vienna (a 5 hour-plus flight), tracked down Saunders, acquired the materials to booby trap the cafe doors (or had planned this ahead of time - unlikely) and set the trap up well in advance of he and Bond getting to the fairground. There was nowhere near enough time for all of that to happen without Necros having psychic knowledge of Saunders' movements.
Continuity mistake: Dick Jones brags (admits?) to Robocop, "I had to kill Bob Morton because he made a mistake. Now, it's time to erase that mistake" while Robocop is crouched on the ground, not only looking away from him from across the room, but also Robocop's eyes are in a vertical position. In the playback, Jones is facing the camera as though it were videotaped or filmed in a studio. (01:10:50 - 01:35:10)
Plot hole: In the unedited video footage of the helicopter incident shown to the crowd, the last shot of Arnie getting knocked out is seen from his perspective and as such could never have been filmed by any camera.
Revealing mistake: Riggs handcuffs himself to the depressed businessman. They jump off the building but they're not handcuffed to each other anymore. They used plastic cuffs which could separate during the stunt in case anything went wrong. They break just as they jump, so they grab each other's hands to stay in contact. After they land the cuffs are attached again. (00:31:00)
Visible crew/equipment: When the trio are driving to the City Deposit/Federal Reserve Bank, in the shot just before hitting the white/red booth, the extended crane arm with the second camera and seated cameraman are visible behind the booth (for filming from opposite angle). (01:03:25)
Continuity mistake: Near the end of the movie, right before the semi-finals, they say that only eight men are left. When they introduce the men, they only call out six names.
Factual error: If the Russian cosmonauts need special suits to survive out to space, so should Lacey when she is taken by Nuclear Man. (00:02:50 - 01:20:20)
Revealing mistake: Mac and Dillon go after the Predator. The Predator is sitting in a tree, and Mac points him out to Dillon. They both agree that they see it and take position. Mac crawls underneath the alien and is killed by his laser. The Predator then sees Dillon and lasers his arm off. Dillon's arm falls to the ground with the gun firing. Quickly Dillon turns and reaches for the machine gun around his neck. When he turns you clearly see his bloody right stump and his right arm sticking out the bottom of his jacket. [Note: As far as I can work out, this has been cunningly edited out of the UK DVD version].
Continuity mistake: In the opening scene, Gunnery Sgt. Hartman is making his speech and passes by Privates Cowboy and Joker on his way to the other side of the barracks. On his way he passes Private Pyle standing to the right of Private Joker. Later in the scene, when he rushes over to confront Private Joker and then moves on to Private Cowboy and then Private Pyle, Private Pyle is on the left of Private Joker. (00:02:00)
Visible crew/equipment: When the guy falls off the cliff and splats on the rocks below, if you watch it in slow motion, you can just see an orange bucket appear for a few moments which chucks the blood in the air. (00:23:25)
Revealing mistake: When Jack is hanging out of the truck you can see him standing on the hood of the car which Lydia is driving. At some points we get camera view from the back seat of the car. In some angles the mirror inside the car disappear. This is to prevent us from seeing the camera. (01:04:15)
Continuity mistake: When Hi, Gale and Evelle are sitting in the trailer talking about robbing the bank, watch the newspaper on Hi's lap. It goes from being folded to being fully opened in his hands between shots.
Continuity mistake: In one of the first scenes with Joe and Curtis reporting to Capt. "wild Bill", Joe and Curtis are just getting ready to walk out of the office. But who's that playing Joe? Certainly not Michael Dudikoff! The next shot Curtis and Joe are comming out of the office and there is Michael Dudikoff again. (00:11:55)
Continuity mistake: When Sam goes into "The Sinker" bar, he goes over and talks to Stacy at the table. When he slips Stacy a photo of the Cherry 2000, between a wideshot and closeup the glasses on the table around Stacy change, as he looks at the photo. (00:22:05)
Continuity mistake: In the car chase scene, the escaped convict and police are exchanging gun fire between cars. In the different shots of the police car, the bullet holes in the windshield appear and disappear several times. Also, when three shots have been fired at the police car there are four bullet holes in the windshield.
Continuity mistake: When the two cops pull the stripper over, their car stops in the middle of the road. When Beck and Gallagher pass them later, however, their car is closer to the pavement. Their car moves yet again when Beck looks back at them out of his window. Also notice that three headlights are now on, including one that the stripper blew out. (00:51:30)
Visible crew/equipment: As Sierge is wrestling with the bear, the shadow of the camera and camera man are visible on the bear. (00:17:55)
Revealing mistake: The Eternia out-door scenes depicting the conquest of the Castle Grayskull area are actually one long shot subdivided into smaller parts. Look at the captured Eternian soldiers marched to the castle; they cover very little distance between the shots.
Continuity mistake: When the four men are shot at the estate gate there's desk behind them with a hat lying on it. During the shooting the hat gets blown away, but in the next shot from the other side the hat is back in place. (02:00:50)
Audio problem: In the mansion, the boys open a secret passage and fall through the floor. They scream after shining a flashlight on a skeleton. Eugene then can be heard whining that he wants to go home, but his mouth is not moving.