Plot hole: The fearless trio is in the watch tower when the hillbillies set fire to it. Realizing their fate if they stay, the three then jump out the window and onto nearby tree branches in order to escape the blaze. After escaping the towering inferno, it seems that the fire dies immediately. These three don't go far after jumping and are in the trees for some time. Shouldn't there be a great glow and lots of noise and smoke from the fire as the watch tower burns down? (00:53:45 - 00:56:00)
Plot hole: When the deputy arrives at the sheriff's house, Michael gets out and leaves the door open. The deputy comes out to the car and sees it open. And he thinks nothing of it, despite knowing he didn't open it. Logic would say, "Well someone else opened it."
Plot hole: Following Glen's death, Nancy tells her father to come across the street in 20 minutes to catch Freddy. She then goes to her house, checks and sets her alarm clock, and proceeds to rig the entire house with booby traps, including filling a light bulb with the contents of several shotgun shells, and has a heart-to-heart talk with her inebriated mom. When she gets back to her room to go to sleep, she checks her clock again. The time on the clock has advanced only ten minutes, not nearly long enough for everything she did.
Plot hole: George Lebay says that his brother died "6 weeks ago" inside Christine and that's why he's selling it. Later that evening after Arnie leaves his house and goes to Darnell's, Will Darnell says he "knew a guy who owned a car like that" and "the bastard killed himself in it." If it's only been 6 weeks since his death, shouldn't Darnell have recognized the car? It's not like there were lots of red Plymouth Furies (custom order color) running around the small town, let alone the USA, even in 1978. (Also considering how production even had a hard time finding them for the movie).
Suggested correction: He says he knew a guy with a car like that. It doesn't have to be the same colour or even the same generation. Just a Plymouth Fury.
Darnell basically said he knew THE brother of Lebay, not just some guy who owned a similar car. Darnell described Lebay's brother based on the story. Again, it was him, not just some other guy.
Plot hole: Not far into the movie, Starla decides to check out the basement to see what Grant's been up to. As soon as the door is opened she reels from the stench and we discover that it's full of rotting meat and dead animals. In reality, the whole house would have smelt like an abattoir for days before hand and the stench would have permeated out into the neighbourhood. A non-airtight wooden door would not have kept that kind of smell located to the basement only.
Plot hole: It has already been mentioned that a certain shot reveals that Sidney isn't wearing the bullet-proof vest when she should be. Further to this, most of the shots in the climax sequence make it impossible for her to be wearing one, as you can see the contours of her chest throughout. A bullet-proof vest would flatten the appearance of this.
Plot hole: In the institute, Will's friend gets out of his room to get the guard's keys. He couldn't have gotten out of his room because there isn't a handle or door lock inside the room.
Plot hole: Sang-hwa forces a zombie inside a toilet stall. The zombie begins to bang on the door violently and Sang-hwa has to hold onto the door in order to stop the zombie from getting out. However, it is revealed later on that the zombies do not attempt to attack the humans or react violently or aggressively if they cannot see them. If this is the case, then this scene of the zombie banging on the door even when it cannot see any of the uninfected humans contradicts the rules that are established later on. (00:25:48)
Plot hole: After his mother's death, Peter sets a camera up outside her therapist's office, so he can see who goes in and who comes out; he thinks his mother's killer might be one of the doctor's patients - a tall woman with long blonde hair. All he sees is people going in and people coming out, and then he sees her - the tall blonde. Problem: He never saw her going in, only going out, which is critical, because the killer is the therapist - a tall man - wearing a long blonde wig and make-up. Of course no-one says anything about "We never saw her going in, only out, so it must be the therapist!"
Plot hole: Laurie calls the police from 1987 Winchester drive, and gives them that address. Yet the police responding to the call go directly to 1960 Winchester drive - where Laurie has run to and is now hiding - even though it's on the other side of the street and several houses down. (01:31:30 - 01:33:40)
Suggested correction: Initially Laurie sends Lindsay across the street, back to the Doyle house to call the police. It's possible Lindsay gave the police the Doyle's address (since that's where she was calling from). Since that call was likely made before Laurie made her call, that explains why the police first show up to the Doyle's house (responding to Lindsay's call) and Bracket shows up minutes later at the Wallace's house (responding to Laurie's call).
Plot hole: When the Grundel explodes near the end, Rowan looks out the window to see Uber Jason floating towards the rescue shuttle, only to be grabbed by Brodski who happens to fly sideways at a high rate of speed. Now provided it's feasible that Uber Jason can survive an immense explosion, how Brodski not only survived the explosion but managed to wind up away from the spaceship and far enough off to the right so as to catch Jason in mid-space is beyond me. (01:22:15)
Plot hole: The dead young girl who wears white has hemophilia (uncontrollable bleeding), and her mother states that she's scared of all sharp metal objects (scissors, etc.), yet she goes to play in an old abandoned steel mill all the time.
Plot hole: In the end, when Charlie is advancing on Emily while turning his light on and off, the final time he turns it on, Kathrine is in front of Emily. How could she get there so fast without being heard? There's at least 4-5 inches of water that would make sneaking very hard.
Plot hole: Kazam is supposed to be a math genius, something that the plot hinges on, but he makes several mistakes when calculating the number of prime factors to find out whether a room is trapped or not. He says that 462 has three prime factors, when it has four, that 206 has four when it only has two and that 563 has two and 911 has three when both are actually prime numbers.
Plot hole: At the end, there is an explosion large enough to destroy and sink an entire ocean liner, but Julianna Margulies, who was sitting right next to where the explosion went off, not only lives, but is virtually unscathed? Yeah, right. (01:19:00 - 01:20:35)
Plot hole: It seems unlikely that Debbie would have managed to take the photographs of her husbands' murders she shows the Addams family at the end, especially considering the angle of the shot of the surgeon. He's not looking at the cam so she wasn't holding it.
Plot hole: Peyton had his face burned in the explosion. In fact, he basically lost his lips, so he should not be able to talk very easily. While he could probably learn to speak normally again through other movements with his mouth and tongue, he does so too quickly to make logical sense. And his uncanny ability to almost perfectly mimic his enemies could probably be learned over time, but again is too quick to make sense.