Continuity mistake: By the end of the movie, when Lucy is sitting in the chair and her skin turns black, we can see her arms slowly turning black as well. When camera cuts away and shows Lucy from behind, her arms are naturally white again.
Other mistake: When the blue van rolls over, and they turn around to go pick them up, they park like 20-30 feet from the van for no reason, instead of right by it, seemingly just to have a tree block their path, then decide to run into a church with really big stained glass window and wood pews while a fire tornado is just outside. Rolling the van back upright, all the TVs and equipment inside the van seem to be working just fine.
Continuity mistake: When Penny prepares to lay down on the ice next to Judd, the back of her sweater is already wet from previous takes.
Visible crew/equipment: When Harry and Lloyd first arrive at the Ken Convention in El Paso, there is a shot of the building. Lloyd walks into the building, opening the door. In the reflection, a large light can be seen, as can some of the crew.
Other mistake: In the final scene both at the start when Fletcher is walking on stage and in a shot during "Caravan," just after Andrew mouths FU, when Fletcher puts a hand under his jacket the shot goes forward and then immediately shows the same footage in reverse. (01:27:55 - 01:32:45)
Audio problem: Murph's dialogue doesn't sync with her mouth at the lines "you hate farming, Dad." (00:17:43)
Continuity mistake: When Andre and Chelsea are talking together on the subway train, the extras behind them constantly change back and forth.
Revealing mistake: When Viggo pushes the car off the edge and it hits the ground, as it rolls you can see that the engine/transmission, drive shift and tank have been removed. (01:26:00)
Deliberate mistake: Despite taking place for at least three years (prior to the arrival of Thomas) in an isolated post-apocalyptic setting, the boys in the Glade have professional looking hairstyles, not the least of which are Minho and Gally, who both have short hairstyles that look evenly cut and professionally maintained.
Other mistake: In the book Hazel is reading near the start of the film, the word 'to' is used 4 times in a row.
Other mistake: At end of movie where there are captions describing how the lives of everyone turned out, for Louie it says "after years of SERVERE PTSD..." instead of "severe." (02:10:25)
Continuity mistake: When the family turn off the museum electrical system and then run away, their shoes are dry and do not leave wet footprints on the floor. Only when Millicent checks the electrics do the footprints appear.
Factual error: After fixing Emily's car, James explains to her that someone must have poured sugar in her gas tank, and besides cleaning the gas tank, he will also have to replace the fuel filter and the carburetor. That would simply not happen: As several tests show, 'sugar in the tank' is a complete myth that will not cause any engine problems. If anything at all would happen, it would clog the fuel filter, but never destroy a carburetor. And even if it would, it could not on a Emily's car - since it's a Fiat 500 and (like all modern cars) it has fuel injection, and does not even have a carburetor. (00:14:00)
Revealing mistake: When the 13-year old boys are "driving" the car to chase after Echo, the car is not being driven at all (but on a tow-truck) because we can see that the gear lever is in the "park" position.
Continuity mistake: Azog kills Fili with his arm sword, running him through from back to front. In the next moment, when Azog tosses the dying Fili off the ledge, we see the arm sword - and it is shiny, clean and spotless.
Continuity mistake: In the shot before Josh hands in his preregistration sheet, he is not wearing his cross necklace around his neck. It was in shots prior to that, and is the focal point of the scene with the preregistration sheet. But in the shot where he is just walking, his clothes and all are the same, but no necklace. (00:03:30)
Continuity mistake: On the airplane, the shark bites off April's hand at about the wrist area, but when Fin pulls the gun in April's hand out of the dead shark, the severed limb is an entire arm up to the elbow.
Other mistake: At the beginning, when one bad guy is sitting on a bench with a newspaper, we can read the date October 21, 1959 at the top. But, we also read Nov 3 1970 on the same page, under the mugshot of the Boss being released from jail. (00:04:20)
Continuity mistake: When Cheryl emerges from the store and begins talking to the club representative distributing flyers, the lemonade she is holding has the cap off in one shot, then on in the next. It switches hands and then disappears entirely. The flyer she holds also switches hands.
Continuity mistake: There is a scene where the family is talking in the kitchen while Colton is drawing a picture. The picture he is drawing changes suddenly as well as the color of the crayon in Colton's hand during a split second shift to another character and back to Colton.