Character mistake: John would have no reason to ask the CT technician if she had any results. He says "that was a long one," indicating he's had this done before and should know it typically takes around 24-48 hours to get results. (Likely just a line of dialogue added for the benefit of the audience, who may not know.)
Character mistake: When nurse McTavish checks mum's pulse, she uses her thumb. Any nurse worth her salt knows that thumbs have their own pulse and that one needs to use the index and middle finger to get an accurate pulse. (00:30:10)
Character mistake: Ginny is supposed to be put head first into the ambulance, not feet first. All the monitoring equipment is in the front of the head. (01:24:20)
Character mistake: Doreen/Mom told Rose she'd be back from the store "in a jiffy." Rose asked, "How long is a 'jiffy'?" and Doreen replied "in about an hour." "Jiffy" typically means VERY fast (perhaps as short as a nanosecond) and, even if people have different perceptions of how much time a "jiffy" is, an hour is excessive by general standards and does not reflect its true meaning. (00:32:50)
Character mistake: Shiwan Khan uses mind control to make Nelson commit suicide. Later, when Lamont is talking to one of his agents, the agent talks about a murder at the museum.
Character mistake: The news article on the murdered gentleman David Carradine discusses has the word existence spelled wrongly. It says existance. (00:37:57)
Character mistake: When Marisa leaves the diner, you can see the door has a "Push" tag. However, the door opens inwards, and in fact to go outside she has to pull. (01:08:00)
Character mistake: When Chafuka is controlling the zombie Barry with her voodoo doll, he's supposed to be repeating her words so precisely that he even imitates her accent. But when she says "that darn fool paper, it fall on the ground," Barry repeats it as "The darn fool paper fell down to the ground."
Character mistake: When Harrigan is watching the surveillance video by Bill Paxton he states that the helicopter is a silver Alouette when it is actually an AS-350.
Character mistake: Remy mentions that the insects are part ant, cockroach and termite. She dismisses the mantis side, which allows it to mimic.
Character mistake: Given Billy still remembered and recognized him it seems strange Kate doesn't when she mistakes Daffy for Gizmo.
Suggested correction: Billy spent significantly more time bonding with Gizmo in the first movie - days and days. By contrast Kate had very little actual time with him.
Character mistake: Early in the film we are repeatedly shown the alien character flirting happily with various men, relaxed, confident, even socially forward, in fact often more articulate and socially at ease than the various Glaswegians she encounters. Yet later on, inexplicably, all this social nous mysteriously disappears and she is completely baffled and blindsided by the simplest of social interactions, almost a mute. Since the film has virtually no plot it's hard to see why this jarring turnaround should be so.
Character mistake: In his opening prologue, Burt says the Graboids have been contained to the Northern Hemisphere, showing a map highlighting the Graboid attacks of the first film in Nevada and the second film in Mexico. However, it overlooks the Graboid/Shrieker attack in Argentina, in the Southern hemisphere, shown at the beginning of Tremors 3, an incursion Burt personally put down. It's not like it was classified - characters in that movie talk about it being reported by CNN, and characters in the Tremors TV series talk about it as well. And it's not like Tremors 3 is no longer canon, since Burt makes two references to being swallowed by the Graboid in that movie (which also becomes a plot point in Tremors 6).
Character mistake: When Cain is attempting CPR on the flatlined patient at the beginning of the film, he tells the other doctor, "She just needs a little more time for the drugs to circulate." Circulation stops at the moment of flatlining. (00:05:25)
Character mistake: Zoe states that Lilly's condition is very contagious and will spread through the camp if they don't go out and get the proper medical supplies they need. She puts Lilly in quarantine... and then proceeds to visit Lilly with no protective equipment. No mask, and even touches Lilly with her bare hands before going back out to the rest of the people. (00:19:20)
Character mistake: There's no way that using a regular needle and thread to sew up that wound would work the way it's shown. Anybody who knew what they were doing - which John Cusack is portrayed as knowing - would also know that using unsterilized materials and instruments without a sterile field from an uncleaned massive open wound is a great way to kill your patient.
Suggested correction: The main plot of this film takes place inside the head of a murderer with dissociative identity disorder. The fact that stitching up a wound in that matter wouldn't work is irrelevant to the fact that it is how Malcolm is playing out the scenario in his head.
You're making a good point to invalidate a "character mistake", but couldn't the entry be reclassified as a "factual mistake" and stand as written?
Character mistake: When they're making the protection circle they make a star of David and not a pentagram, 6 points in a star vs 5 points.
Suggested correction: I don't think there was anything in the movie that dictated a pentagram had to be used. In the book of protection rituals they were using, the particular ritual showed a picture of the star of David they needed to create, so that's what they used (plus salt).
To add to the correction, what the mistake refers to as "Star of David" is a hexagram and the use of hexagrams in the occult are not uncommon. You can find salt protection circles that use the hexagram.
Character mistake: The ref says there's no rules before McClure fights Whiplash but she tries stopping them later.
Character mistake: When Michael goes to the antique shop, the sign out front is spelled wrong; it reads "anitques."
Character mistake: Reina asked Cory if they could "do that thing" because it was helpful for her medical school training. Reina then put a raw slab of steak/meat across his forehead and made slits in the meat as well as jabbed at it. A medical student studying to become a brain surgeon should know about and practice the safe handling of raw meat. (00:23:10)