Character mistake: Mitch states that he is Pisces then goes on to state that his birthday is 25th of March. The Pisces period goes from 19th February to 20th of March. Mitch would actually be Aries. (00:35:00 - 00:37:00)
Continuity mistake: At the end of the film we see stuff being crossed out in a notebook. The lines that are drawn through the words keep changing from being perfectly straight to being at an angle.
Continuity mistake: There is a scene where she accidentally stabs someone - she gets blood all over her from the stabbing and then in the very next scene is wearing the same shirt without blood stains.
Continuity mistake: Everly puts the phone down next to the necklace she grabs. The phone is facing up, but after she wears the necklace, it's facing down. (00:06:40)
Continuity mistake: Treat Williams is drinking a brown liquid from a glass (scotch?) while accusing Gina Carano of having something to do with his son's disappearance. Shortly afterwards, the liquid is a different color and the glass is much more full. (00:41:40 - 00:42:40)
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 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.
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.
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.
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.
Visible crew/equipment: When the little boy is lying in bed looking up at a hole in the wall you see a creepy hand move, the while time, if you look closely, there appears to be a human hand with human fingers to the right of it in the darkness.
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.