Continuity mistake: When Christine is fixing herself after the guys smashed her up, her front end is shown to be perfectly straight for its entire width and the hood is missing. Near the end of the scene, the front end is shown crushed and unfolds again, and the hood appears from nowhere.
Continuity mistake: Eddie drives a 1957 Chevy convertible off the bridge. A scene showing the car being fished out of the water clearly has an older vehicle dangling from the line.
Suggested correction: The car pulled onto the bridge is absolutely a 1957 Chevrolet convertible.
Continuity mistake: After Norman argues with Mr Toomey, before he goes up to the house, you can plainly see the light on in the living room where Mary is sitting. When Norman goes in the house, Mary is sitting in the dark and Norman then turns on the light.
Revealing mistake: The outline of the blood pack is visible under John's shirt when Stillson's body guard shoots him. (01:37:35)
Continuity mistake: When Meg comes up to Angela, taunting her, Angela's head position and the look on her face changes in each shot.
Visible crew/equipment: Naomi Arai snuck back home from the window. When she walks down the stairs to go in the dining room, you can see on the upper floor wall to her left the shadow of the camera crew following her. (00:01:20)
Plot hole: It seems unlikely any mental institution would let a patient out to visit home for any length of time as happens in the movie with the killer and his mother.
Suggested correction: Unlikely, but still possible. Almost every workplace has a situation in which a person is bending the rules.