Continuity mistake: On the end of the movie, when Harrigan is leaving the cave where the alien ship was, there is no way a ship that big could pass through such a small hole. (01:39:00)
Continuity mistake: In the slaughterhouse scene, Danny Glover's character pulls out a shotgun and blasts the Predator several times, knocking it flat on his back. Just as soon as you see the Predator hit the ground, you can see his mask start to fly off as though it's loosely attached. In the next scene, Danny Glover has to put some effort to pry it off, when it should have flown off in the first place. (01:18:45)
Revealing mistake: In the slaughterhouse scene, look carefully after the predator throws the disc to Keyes. The disc slices the beef that are hanging, but just before it slices Keyes, there is a split-second stop. (01:21:50)
Revealing mistake: When the Predator runs out of the bathroom after doing minor surgery on himself, you can see that when he punches through the bathroom wall and into the living room and from the living room into the hallway, that both sets of doors had been pre-cut to achieve this effect. Even with the amount of force applied by the Predator, to do this considering how powerful it is, the wooden slats that were used in the old days to give homes extra strength and to help plaster adhere to walls would certainly have been more rugged looking than they were as in the movie they are neatly cut into the shape that the Predator, had to go through. (01:29:55)
Continuity mistake: Notice King Willies teeth before he is killed. They are nasty looking. After the predator cleans up his skull, the teeth are white and shiny and also change size. (00:47:00 - 00:49:00)
Continuity mistake: At the warehouse, when Harrigan and the other officers are looking at the carnage caused by the Predator, Danny points out the dead Columbian hanging from the skylight. The camera cuts to show the man hanging dead from the skylight, and you can see that he has a good amount of blood running down his body. When Harrigan is ordered downstairs, the scene cuts again to the body being hauled up by the Predator, except now the amount of blood has increased tenfold, looking almost like someone threw a bucket of blood on the corpse. (00:13:40)
Revealing mistake: When the drug lord falls from the roof he lands on a table yet it doesn't collapse under his weight. The building was pretty tall. (00:10:25)
Continuity mistake: In the beginning, after the gang retreats into the building, you see what appears to be the leader sniffing from a golden container. After a quick cut to the gang getting ready, you see his moustache covered with white powder. After another cut, a closeup shows his moustache is clean, way too quick to have cleaned up.
Visible crew/equipment: When the Predator is attacking the Jamaicans in the penthouse, you will see the guy who gets pinned to the wall with the net propelled backwards. We are led to believe that it is the force of the Predator's weapon - not so - it is the bungie cable attached to his trousers. (00:24:55)
Plot hole: When Harrigan and Captain Pilgrim leave the head Captain's office after being told not to impede Agent Keys' investigation, Harrigan then spots Keys and goes and roughs him up, shouting and generally making a nuisance of himself. Pilgrim was only just behind him. Harrigan's actions have caused everyone else to be quiet, so it's not as if Pilgrim doesn't know that Harrigan isn't manhandling Keys, yet he does nothing to intervene, especially in light of the meeting the pair of them just left. (00:38:30)
Continuity mistake: When the Columbians are in the armoury near the beginning, they all look up as a skylight shatters. In the slow motion shots, you can see the leader turn away from the glass. But, then it shows him in a closer shot, and he's still facing the falling glass, and falling back away from it, shielding his face with his hands.