Factual error: Our heroes find a boat belonging to shark poachers, smashed to pieces by the Meg. Floating about in the debris are the bodies of a number of dead sharks. Sharks do not have swim bladders and dead sharks do not float - they sink.
Other mistake: The construction of a staircase does not require a large nail at the site shown on the steps. Furthermore when Emily snags her clothes basket on the stairs it lifts a small nail up. How did it grow into a 2 inch fat nail?
Continuity mistake: In the end, when Michael has grabbed Karen's ankle and is trying to pull her down into the basement, Allyson grabs a knife off the floor and stabs him. However, if you watch very closely, you can see she's already holding the knife in one shot before she grabs it. (It's the shot right before Laurie screams "I've got you!" to Karen.) You have to pay attention because it goes by quickly, but you can see Allyson lifting the knife into frame for a split second, even though she doesn't pick it up off the floor until about 15 seconds later.
Continuity mistake: When Anne breaks up with Eddie on the sidewalk right after they get fired from their jobs, she approaches him and drops the box she is carrying. A ceramic mug falls out of the box. There is both visual and audible confirmation. After putting her ring in his shirt pocket, she bends to pick up the empty box and proceeds to walk away without also retrieving the missing contents. (00:14:45)
Factual error: During the plane ride into France, the Paratroopers are holding/carrying their weapons by their sides. In reality, their weapons (M1 Garands, B.A.R.s, etc.) would be carried in special "bags" strapped to their parachute harness. This not only protected their weapons, but also secured them to their person.
Continuity mistake: When Sister Irene's habit is ripped at the back, you can see a bra strap on her left shoulder which disappears when she is seen at the front and when the camera is closer to her back (when she has the pentagram carved into her).
Audio problem: As Annie is trying to leave Joan's house and she starts to give Annie instructions on how to do the ritual, it's obvious the audio for Joan's lines was dubbed in in post as a lot of her speech doesn't quite match up with her lips. Especially when she's saying "Your whole family needs to be in the house". (01:08:00)
Continuity mistake: When she is in the boat she takes off her blindfold entirely, but after some talking the blindfold is around her neck all of a sudden.
Character mistake: When Logan tries to use both his and his mom's phones after her fingers were broken by the Man in Black, he throws them in disgust when he finds the SIM cards have been removed. However, every cell is capable of placing a 911 call regardless of whether a SIM card is present or not.
Plot hole: As the evolved Predator's ship takes off it leaves Casey Bracket alone in hilly forest terrain. The ship then flies a long distance before crashing and the Predator and McKenna start fighting, just for Bracket to show up and help out of nowhere. Impossible for her to cover that distance that fast in hilly forest terrain.
Revealing mistake: Baca is using a pistol to shoot the zombies towards the end and still has this same pistol at the end. When he's on the ground about to shoot himself to stop from turning, it shows a close up of his pistol which reveals it's a 6mm BB gun. (01:20:15)
Character mistake: During an intermission following Dmitri's revenge after the attempted hit on him, the Chief of staff discusses the data with Dr. Updale. There's a pie chart in the screen in the background, and the segments are; 5%, 25%, 16%, 14% and 50%, which add to...110%. It's not a pie chart, it's a pie and a slice. (00:50:15)
Other mistake: Daphne's dad drops the Legitimate Tulip badge in front of her so she'll avoid getting hurt, but when we see him do that, he does it before the warning for the ball is heard and seemingly not looking at the danger (especially in the second shot, when he is peeking from the corner). So his action makes no sense. (00:16:55)
Other mistake: At the end of the movie Lorraine has to remind Elise that she helped her once, implying they haven't seen, or spoken since. When Elise first meets Josh in the 1st insidious she tells Josh that her and Lorraine have been friends for a long time, implying they talk or see each other regularly.
Suggested correction: That's debatable as the word "friend" does have to do with semantics. I have friends I have not spoken to in a long time, or speak with rarely, but still consider them friends due to our history. Others would say that's not a friend as that's not what they think of when they hear the word "friend." So it does depend on the individual person. It's also quite possible this is what they told Josh as the cover story for why she was contacted since they initially didn't want him to remember his past.
Other mistake: The RV's cassette player has some odd features (some of which I've never seen on a cassette player). There's a "push button" for "loudness", not "volume." There is another "push button" labeled "MO ST" - not sure what these mean. The slot for the cassette tape looks wide enough for a VHS tape. (00:11:15)
Suggested correction: There's nothing wrong with the stereo. The cassette slot is the normal size for that configuration on an 80's cassette car stereo (they're in an '87 Suncrest). The loudness button was also a common feature for that era. It boosts low and high frequencies at lower volumes (the stereo still has a volume knob). MO stands for "mono" and ST stands for "stereo."
The slot looked way too wide, even for the 1980s. I would have guessed that the "ST" meant stereo, but wouldn't that be referring to the AM/FM radio, not the cassette player? (Thanks for the "MO" clarification). [Features were still on the odd side.].
Continuity mistake: After Asher is separated from Quinn he's looking around a room with a flashlight and finds the killer. We can see the killer's eyes but a few shots later there is mesh over the eye holes of the mask. (00:52:15)
Revealing mistake: When the doctor with the satellite phone runs to the car, he is being chased by another member of the team, and of course the graboid. Look ahead of the graboid. The path it will take is visible.
Factual error: The police officer that shows up does two stupid things in a row that real police would never do. When investigating a kidnapping, he calls in what the car was they were looking for. Which he sees. Instead of calling for back up, or even mentioning to dispatch that he found a car that looks like it, after coming from a murder scene at a gas station and following a map left behind to this spot, he approaches the car alone, without calling for back up, or drawing his weapon. Shortly thereafter, he finds the kidnapped boy inside the car, who tells him the man who took him is in the house. The officer then proceeds to go into the house alone to look for a dangerous kidnapper without waiting for backup, even mentioning to the kid that his partner is on the way. (00:32:00 - 00:33:35)
Continuity mistake: After a camera shift while talking to Mr. C, Chris' jersey was pulled down more over his pants (lap), but his hands were pre-occupied playing with the string on his hooded sweatshirt. (00:06:35 - 00:06:58)
Revealing mistake: At the beginning of the movie, the protagonists dump the corpse of an agent in the middle of nowhere. The guy is stone cold dead...but you can see the carotid pulse on the right side of his neck, under the fake blood. (00:03:10)