Factual error: When Tripp enters the garage and we see his truck in progress, he states that the truck will have 425 horsepower. The Hemi pulled out of the Terravex truck is not a 6.4L Hemi (only a 5.7L Hemi) and even if it was a 6.4, they only produced 410 horsepower in the heavy duty trucks. The 5.7L Hemi makes 375 horsepower in the trucks and 390 horsepower in the cars.
Factual error: McVay gives the order to cease zigzagging, full speed ahead, but the Japanese sub commander gives the target speed of 12 knots for the torpedo solution. The Indianapolis was capable of a speed in excess of 30 knots.
Revealing mistake: When Gabby and Fin are hanging off the building in Las Vegas, you can see that Gabby isn't holding on to anything in some close-up shots. (00:11:47)
Plot hole: The Chinese army displays a great variety of (often anachronistic) weapons and they spent considerable resources arming and reinforcing the Great Wall to challenge the beasts who have been plaguing their land every 60 years for thousands of years. but despite having records of magnets being effective against them, with magnets being well known to them for centuries (early magnetic compasses were available in the IV century BC, and the movie is set in the XI century) they made no use of that at all.
Factual error: The present day "Grimsby" train station shows electric wires and trains. The real Grimsby only has diesel ones.
Character mistake: Despite portraying a highly trained Special Ops marksman, Seagal repeatedly holds his rifle incorrectly, resting the butt on top of his shoulder instead of braced against it, making proper aiming and recoil control impossible. He also switches his weapon between hands when turning corners, a tactic no real special operator would ever use in close-quarters combat.
Visible crew/equipment: A cameraman is in the bush at the start between the preacher and his mule. (00:01:06)
Revealing mistake: Set in Pittsburgh, PA, scenes were obviously filmed out of sequence. Many scenes were "out of sync" with the snowfall, whether in progress or amount (if any) already accumulated. For example, there was no snow downtown, but views from the helicopter showed snow-cover around the nearby parkway (Route 376). In another scene, it was snowing when Ryan turned his Jeep into a downtown road that was covered with at least one inch of snow; switching to a "live" newscast, the sun was shining outside.
Continuity mistake: While Jax is held against the wall by two of the Furies it shows her bare feet held off the ground. As she moves across to Sinbad after he plunges the sword into the third Fury she is wearing flip-flops. (00:29:17 - 00:29:54)
Continuity mistake: At the beginning of the movie, the hunter is looking for his dog. The rifle on his shoulder keeps changing position, being upside down or not - which is easy to spot because of the big scope. (00:01:30)
Continuity mistake: The chef at the airport stabs someone, but the knife blade is clean afterwards; moments later he stabs it through the valise, and it is covered in blood.
Continuity mistake: When Masovich kills Paolo, we see the slide stay locked in the open position. But in the next shot the slide is closed.
Continuity mistake: In a second view at a different angle of the bank employee being shot, one of the doors that was shattered in the original shot is not shattered in the second shot. (00:03:02)
Continuity mistake: The crew arrived at the volcanic island in turmoil, and are talking with the local captain. The captain asks them to carry also some of the dead people, and they start asking him what the plan is, if there's one at all. The pass at the neck of the captain shows the side with the symbol in one shot, the blank one in the next. (00:25:10)
Continuity mistake: The protagonist is fondling his pregnant wife in bed when she pinches his nose. Between the two shots the blanket covers /uncovers the baby bump, and her hair is bunched on the pillow in entirely different ways. (00:01:40)
Continuity mistake: When Kurt and Kavi are washing clothes, the clothes change position on the line, specifically the red shirt at the end and the shorts Kavi hangs up. The red shirt is twisted around the line, but in the shot of Kavi hanging the shorts, the shirt is hanging perfectly straight down.
Continuity mistake: After the credits, Tom Hopper sees and hears a bunch of helicopters and calmly walks indoors. He then addresses the waiter raising his left hand before the cut. In the next wide shot though we see him with a right hand raised that reaches for the champagne tray and grabs a glass. He says "Thank you" in a third shot, same angle as the first one, and in fact, the champagne flute is in his left hand now. (00:02:50)
Revealing mistake: Despite Sigourney Weaver supposedly having had her fingers cut off if you watch her when she's in her straitjacket you can see her fingers moving around.
Continuity mistake: The gang Bo is reluctantly part of gets to Maurice's crib where he is playing cards with his homies. The red jacketed one is defiant, and grabs a handful of red and blue chips in front of him tossing them in Angelo's face. But if you check out of the table in the wide shots before this occurs, you'll notice that red chips were never in the stack in front of him to begin with. (00:19:05)
Continuity mistake: When Batman and Batgirl are about to have sex on the roof, Batman lets his left hand slip down from her back to her butt. In the next shot, it's on her back again.