Revealing mistake: At the start after the main title appears you can see the outside of Haddonfield University and you can easily tell that the building is a digital composition. (00:16:10)
Other mistake: When Freddy and Sara walk down the stairs after hanging Michael Myers with the camera cord, neither of them notices Jen's head lying on the floor. You'd think that they'd react in some way to this. (01:11:15)
Continuity mistake: When Bill talks to himself in the mirror Michael bursts through the wall and grabs him but after you see the quick scene with Freddy and Nora having their glasses of wine Michael is completely out of the wall when he stabs him. (00:43:30)
Continuity mistake: When Freddy enters the kitchen dressed up as Michael Myers, he has a knife in his hand. Moments later, you see him yell at the real Michael Myers. Freddy has no knife in his hands and you didn't hear or see him put it down. (00:51:00 - 00:52:30)
Continuity mistake: Halfway through the film, we see Michael Myers walk into a room immediately followed by another Myers. Both are dressed nearly identically in a blue jumpsuit. But as soon as the first one turns around and we learn it's actually Freddie, the shot changes to Michael and back to him and he's wearing his jean jacket, seen in the rest of the movie.
Factual error: School emails are .edu, not .org.
Visible crew/equipment: At the end of the film one of the news reporters asks how Freddy is feeling at the moment - when he says this you can see a black object covering half of the screen. (01:19:40)
Continuity mistake: When Michael Myers has Sara cornered, he rotates the knife in his hand so the blade is pointed down. After being knocked backward by Freddie, Michael advances forward and once again rotates the knife to point the blade down, yet he never changed it back.
Plot hole: Bill was killed in Judith Myers' bedroom, but his body was discovered on the stepladder leading to the attic. Wouldn't there be a noticeable trail of blood leading from the bedroom to the attic? Michael might hide bodies but he doesn't clean up after himself.
Continuity mistake: Near the end of the film, Deckard is communicating to Sara's handheld device where Michael Myers is in the house. When Deckard tells Sara to "GO NOW!", the text has changed from small digital text to large bold font and the screen has changed from green to white, similar to a large PC monitor.
Continuity mistake: Freddie has all the cameras cut when they find out he's a fake Michael Myers. When the kids complain to Deckard about it suddenly going offline, they tell him to bring it back. Deckard types at a fast rate, yet not only is there no dialogue box for text to be typed in, the screen remains the same.
Revealing mistake: When Michael is hung from the window, an upwards shot reveals the top of the sound stage the Myers house was built in (top right corner). (01:13:42)
Visible crew/equipment: There's a cameraman visible when the two guys walk into the house party. He doesn't belong in the scene and is filming.
Continuity mistake: At the Myers house when the guy with the black jacket is lighting a candle he uses his right hand then the left.
Revealing mistake: In the H20 flashback when Laurie cuts the head there is no blood from it.
Other mistake: When Donna is in the basement by herself, she sees a picture of Laurie cut out of a newspaper. This is a picture of her from Halloween (1978) when she was waiting for Annie to pick her up. So where did it come from?
Continuity mistake: In the garage Sara falls down and a piece of electronic equipment lands on her. She acts like it's so heavy that it has her unable to move. Yet when Freddy comes to her aid, right before he lifts it off, Sara starts to get up on her own.
Continuity mistake: Nora picks up her phone twice before she makes the call to Freddy in the garage, whilst Charlie is getting killed.
Continuity mistake: After Sara receives a message saying that Michael Myers is still alive on her palm pilot Michael Myers stabs Freddy in his left shoulder but when it cuts to the close ups of the blade in his shoulder it is in his right shoulder. (01:11:45)
Continuity mistake: When Sara is riding up the school pathway on her moped,beside her you see a boy pulling his bike along approaching his friends and he is about half a meter away but in the next shot the boy with the bike is about two meters away from his friends. (00:17:05)
Answer: Or maybe he's thinking that his mission to kill Laurie is done. He's been trying to kill her for a long time and succeeded. No need to continue, but when those kids invaded his house, the killing began again. No one goes into his house, but him.