Factual error: We're told they carbon dated the gold to determine its age. Problem is, the gold hasn't aged by the normal processs - as it's been brought forward in time it will appear to be extremely new. As such carbon dating wouldn't work. Also, carbon dating only works on things that were alive and absorbed carbon-14; gold, having never been alive, could not be dated this way.
Continuity mistake: In the scene when Rudy is holding a colt python to the hotel owners nose, in the next shot, the gun suddenly changes to a smith and wesson revolver.
Other mistake: When Lamont walks into the alley to avoid being followed by one of Khan's warriors, he makes himself invisible, and his shadow vanishes as well. It's well noted at the beginning of the film that his shadow is always visible even if he isn't. Therefore, his shadow should still be seen on the ground and give him away.
Continuity mistake: When Tommy Lee Jones pops into his local Irish boozer for a pint of what is supposed to be Guinness, it is clearly not a pint, it is clearly not Guinness (flat Coke, more like), and the level of said beverage in the glass fluctuates wildly and out of synch with TLJ's swigging.
Factual error: There is a shot with Wesley Snipes and Gary Busey aiming one another just to pull the triggers and discover that the guns are out of ammo. In fact, after the last shot (of the pistol, not the movie) the slide of a semi automatic pistol is retained open by the empty magazine, and doesn't return forward as we can see in the shot (of the movie, not the pistol). The reverse mistake is very common in movies, when the armorer loads just one round to be shot (in the movie as well as the gun) and the actor keeps fighting or menacing with an unloaded, breech opened gun.
Visible crew/equipment: When Li's sons is doing "pushups" on one finger while flying up into the air you see the wire attached to him. (00:29:50)
Factual error: When Julia Roberts drives away from the building where she finds the dead body of the boy with "LD" written on his hand, it is raining heavily. Yet, as she accelerates, there is an extended sound of tyres screeching on a dry surface.
Continuity mistake: At the final fighting scene (David Sloan vs.Tong Po), you can see that Tong Po's hair (a half shaved head with only a ponytail on it) is as fake as it can be: everytime when he moves his head a bit to rough around (sweeping his ponytail around while fighting) clearly shows that he's wearing a special kind of wig attached to his head. That 'wig' is so badly attached that it looks like he's got rimples on the back and on top of his head.
Continuity mistake: In the bus scene, when Stallone goes on the bus the number is 9372, when he kicks the bad guy out of the window the number on the bus' side is 9369.
Factual error: Near the end of the film, after Ditch and Krista use the reserve parachute, they fall in a windfarm. The windmills are spinning fairly slowly. After the fight Ditch pulls Pinkwater's parachute out. The wind pulls Pinkwater back towards the fan. Before he gets chopped up there is a shot of the fan blades spinning very fast and powerfully. A light breeze would not cause these blades to spin in this fashion. A hurricane would be needed for those blades to chop up a human.
Continuity mistake: When Gary Busey is breaking out of prison, there is a part where he runs into a fence and acts disappointed since he cannot get through it. However, if you watch carefully while he is running, in a split second when the fence first comes into view, you'll notice it has doors which are swung open.
Continuity mistake: When Pepper and Sonny arrive at the warehouse on the water for the shootout, Pepper asks Sonny if he wants to lock the truck. When they come back to the truck with Shaw, they immediately open the doors even though they locked the doors earlier. (00:01:25 - 00:13:30)
Deliberate mistake: When the recon team head out of the base they encounter a robot. But it is a probe droid, distinguishable by the lack of a cannon on its right arm. The only probe droid that the lab sent out self-destructed back in the 1970s, the rest were all sterilisation units. (00:39:05)
Continuity mistake: When Tom tells Gail he won't take part in the rafting trip and she sits down on the bed, her hair changes several times between tucked behind the ears and hanging straight in alternating shots. (00:04:35)
Continuity mistake: When Connor is escaping from the psychiatric ward you can clearly see the cameras running tracks on the floor.
Continuity mistake: In the scene where Dhalsim changes the programming, all the computer shots of Blanka show him with normal skin, despite that it's turned green.
Plot hole: This TV movie uses a lot of flashbacks to the previous 4 installments, by having people saying to each other, "Hey, remember that time when we..." a bit more than usual. In the village of the Minotaur, Iolaus remembers the fight from Hercules and the Amazon Women where he dies. That is also the reason why this flashback is interrupted just before that point. But at the end of the Amazon Women story Hercules used magic to jump back in time and change history so that the whole adventure had never happened (next making sure that it would not happen all over again). Obviously they wanted to use some cool action footage from all the TV films. But Iolaus could not remember these events as it happened in some cancelled version of the future. (Hercules remembers, but he wasn't going to tell anyone, and that's what we have to go on).
Visible crew/equipment: When the spheres fly through the air you can see a "dot" following which is the camera.
Revealing mistake: While Noro, a member of a shoeless society, is doing his uphill training you get a glimpse of his shoes, in spite of all efforts to hide his feet in the grass. (00:53:30)
Audio problem: When the good guys finally get the Chevy V8 running, the sound it makes sounds more like a moped than a high-performance engine. It has headers and no mufflers, so it should have been quite loud.