Factual error: Michael boards a commuter train at Grand Central, which then stops at subway stations at 68th Street, 86th Street, and 110th Street along Lexington Avenue. This is impossible.
Continuity mistake: Ron Perlman and Famke Janssen are having dinner on his supposed birthday. The whole meal has several continuity errors, with her fork being at different heights, sometimes replaced by the wine glass, etc. (00:34:30)
Factual error: Spoiler! The cultists burned Mandy alive by wrapping a sleeping bag around her, putting gas on her and hanging her from a metal swing set and setting her on fire. After Red frees himself later and craws up to her remains, it's shown that she is barely a pile of ash with her skull still somewhat in shape when he picks it up. It then crumbles into just ash showing she had been fully burnt to the very center. This would not have been the case with how they burned her. Their was nowhere near enough heat or kindling to keep her body burning long enough to turn completely to ash with no remains like that. She would have died, yes, but would have mostly stayed intact as a single body burnt very bad. Bones, features, charred organs would still have been left behind. (01:04:00)
Factual error: The opening scene shows Cassie and Bryan booking their holiday on a laptop. The dates that they book the holiday home are between May 5th 2018 and May 12th 2018, which means the movie is set in 2018. But later in the movie, when Cassie finds the video of Bryan with the two women on his phone, the date is listed as "Sunday, May 7", and May 7th 2018 was a Monday, not a Sunday. (00:01:05 - 01:10:55)
Continuity mistake: The three besties are in the car at the beginning of the movie, chatting. During the chat, the scenery keeps changing between shots without much consistency. (00:00:50)
Continuity mistake: Waikiki lowers Honololu's gun telling him that the caveau won't open. There's a reaction shot of their hotheaded accomplice holding his gun with both hands and tilted. In the background of the next shot, he's holding the same gun with just one arm. (00:01:50)
Continuity mistake: The position of Don's baseball cap on the table changes two times. Initially, the cap is near the corner of the table with the visor and letter "P" roughly parallel to the front of his body. After he pours beer into his glass, the visor is angled more toward the corner of the table (even though the camera appears to pan around it). When Don brings Mike back to the table, the cap visor is pointed toward Don and is at a differently angle (more parallel to the front of his body again). (00:00:09 - 00:01:47)
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.
Continuity mistake: There are several variations or inconsistencies in Marcus' hair and tie from the time he goes through the metal detector and sits in the courtroom. His hair was consistently "messy", but disheveled right and/or left sides were inconsistent. The tie was fairly snug against his collar at first, but got looser then tighter. (00:54:14 - 00:57:08)
Continuity mistake: Darren is smoking salvia in the first scene in the hotel room. He lies down on the bed; his hand changes position between shots several times. (00:03:30)
Continuity mistake: When young Tiffany is eating ice cream at a restaurant, the amount of ice cream left in the clear glass bowl increases after she eats more. The ice cream in the bowl starts out being about half-full, goes down to less than one-fourth, and returns to about half-full again. (01:02:47 - 01:03:19)
Continuity mistake: The orchids in the vase in the center of the table are spread differently in views of Erasmus or Paul. (01:11:12)
Continuity mistake: Tommy, the truck driver, offers Ray a tip and Ray puts a money box on the desk and opens it. After they discuss him not wanting to accept the tip for a moment and then Tommy walking away letting him keep it, it cuts to Ray putting the money in his back pocket. In that shot the money box has disappeared from the desk, without him ever having touched it again in that scene. (00:18:10)
Other mistake: The view of Katherine's bloody body showed blood running diagonally almost exclusively from left to right, but the Ten Killer slashed her equally from right and left. Blood should have run in both directions. (00:45:05 - 00:46:25)
Continuity mistake: On his way to work, Antonio meets his ex Camilla.During their conversation, as it's particularly evident in the subway stairs sequence, passersby vanish every time the camera cuts to another angle. (00:08:00)
Continuity mistake: In the vault scene arguing/fighting with Gunnar, Taj/Lars had a clump of hair sticking up in the middle of the top of his head during most front views, but not rear views. (01:03:10 - 01:04:11)
Factual error: Three men are having beer one night in the woods. One man says he has a picture of a girl he took the previous Tuesday. When he goes to get the picture (which would be on his phone), he complains that he can't show it because there is no signal reception. You don't need a signal to show a photo you took on your phone. (00:07:10)
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)
Plot hole: When Rupert brought his "secret pen pal" letters from Hollywood movie star John to school, they were stolen by some classmate bullies (and apparently never recovered). Rupert would have been around age 11 (possibly 12) at the time. It is inconceivable that a child could recall enough details from the letters to write a book about them 10 years later.
Continuity mistake: Tom and Hallie are talking in his kitchen about Slender Man after she freaked out during them trying to have sex. He backs up against the island and his left arm goes up behind his back resting on the top of it as he's blurred in the background. The angle cuts to a wide shot and suddenly his arm is down at his side. (01:01:00)