Factual error: The British Major is wearing a RAMC (Royal Army Medical Corps) cap badge (incorrectly mounted). Really, not a British Army Corps known for their sniping skills.
Revealing mistake: Jim parts his hair on the left side. The stacks of his books on display in the hallway include a photo of him with his hair parted on the right side, but otherwise looking the same. Hair that is persistently parted on one side will not easily part on the other side and lay across the head in the same way. (The image was reversed). (00:25:20)
Factual error: The alien drops the video camera out of the UFO from outer space and it falls to earth landing on the ground. This very far drop would certainly have busted it to pieces, if not ignited it on reentry, but when the guy picks it up off the ground, it appears only the screen is cracked.
Character mistake: When Jesperson imagines himself as a Mountie his uniform is completely wrong and is not even the right colour. As it was his ambition to join the force and he has photos of RCMP officers in his cab, it seems unlikely that he would imagine himself in a completely incorrect uniform.
Suggested correction: It's not a character mistake, for the reasons stated; it's a clear factual error from the filmmakers.
It's a character mistake since it's his imagination and, as you stated, it's not something the character would get wrong.
Continuity mistake: Stretch takes the licence plate off the limo just before it's stolen. When he's clinging onto the bumper as it's being towed, the plate is back on.
Continuity mistake: Roy is on his back at one point, seemingly knocked out. A shot later he's suddenly on his stomach before regaining consciousness.
Plot hole: Tom told I.D. Halden, "My grandmother passed a few years ago and we inherited the family house." If there was a mortgage, who was paying it for a couple years? And if the house was inherited, there would not be a landlord, they would not be paying "rent", and owners do not get served with an eviction notice. (There was no mention of a legitimate reason, such as unpaid taxes.) There's a failure to discern home ownership (with a mortgage) from renting a house (which is not "inherited").
Suggested correction: It seems to be that it is about two different houses, the rented one they already live in, and the inherited one which is renovated.
Continuity mistake: At the end when Sarchie is hugging his wife, in one shot the bandage on his arm has unravelled. In the next, it is neatly wrapped.
Revealing mistake: JR is in the weapon container of the crazy dealer, who passes him some of his goods. JR ends up holding in his right arm a MP5K and an M4A1, which combined are about 5 kilos, but then he passes him an M60 Machine Gun, which weighs over 10 kilos and that the relatively diminutive protagonist just handles throughout the scene gripping it with his left hand and making no effort whatsoever. (00:25:20)
Factual error: In a scene where Kat is flying to or from Northern California for college, in the background through the window on the plane one can see a commercial jet which has the winglets of a narrow-body Boeing, which were not introduced until 1998 on the Boeing 737 NextGen, rather than "wingtip fences" of an Airbus which were in use as early as 1985. Eve disappeared in 1988 when Kat was 17, so this would have been 1993 at the latest, when Kat would have been expected to have graduated from Berkeley. In the movie, it is suggested that this was just 2 years after her mother disappeared, so this would have been not later than 1990-91.
Revealing mistake: At the end the sides of the grave (which Jack just had dug by spade) are too perfect. Only an excavator could get such neat sides.
Continuity mistake: Carrie's height changes constantly.