When Nicolas is watching the film strip, he gets fed up and stands. He looks back and clearly is standing in the way of the film's projection onto the screen, but when the screen is shown there is no shadow.
Nicholas confronts one of CRS's employees at the Zoo trying to find out who is in charge. The employee tells him "This is extremely dangerous." Nicholas replies, "No, you don't understand. Right now, I ... am extremely dangerous." at which point the sound of his gun being cocked is heard. He then puts the gun to the employee's neck but the gun is not cocked.
In the elevator scene, Nicholas climbs up and grabs the cables with both hands to pull himself up first. Then after he helps Christine pull her up after him, one of his hand's is clean and no grease is on his shirt.
After the pen spills ink on Nicholas' shirt, he goes in the bathroom to try and clean it up. As he leaves the bathroom, he clearly buttons his coat to cover the ink spot, but in the next scene in the restaurant the coat is unbuttoned again.
When Nicholas returns home at night and enters to find luminous graffiti on the walls and Jefferson Airplane's "White Rabbit" playing loudly, he goes upstairs to the living room to investigate. The scene then cuts to Nicholas running outside to check on the housekeeper, Ilsa. The song is heard continuing to play without interruption, not accounting for the time it would have taken for Nicholas to run back downstairs again.
Daniel Schorr reports the same story twice. "Petroleum processing plant yesterday." can be heard in between Nicholas's first and second mentions of the word "fine." and after Ilsa says "Goodnight, then" to Nicholas.
when Nicholas and Samuel Sutherland enter the room where Anson Baer and his family are having lunch to confront him, Nicholas throws a stack of Polaroids which end up all over the table and the floor. In the next shot the Polaroids have disappeared.
After Nicholas and "Christine" drive away from the house as it's being shot up by the CRS agents, the BMW windows are cracked like a windshield would be. All cars now use safety glass in the side and rear windows that breaks into small pellets any time that they suffer a sharp impact (like a bullet).
Nicholas Van Orten fires Anson Baer because he didn't meet his quota, then he offers him a severance package. Fired employees don't get severance, only if they're laid off. California as of 2018 is a "fire at will" state, so Anson would not be able to sue. So Nicholas had no incentive to offer a severance package.
The CRS building where the climax occurs is depicted as having 18 floors (plus a possible few extra from Nicholas and Christine's runaway from the CRS agents in the building). The Sheraton Palace, used as the setting for CRS San Francisco headquarters, has only 9 floors, half the amount that CRS has.
When the "news anchor" is speaking to Nicholas through the TV, Nicholas begins to pry apart the TV in order to find the camera, and the man on the TV looks directly to his lower-left, right at where the panel is being broken off. This would only make sense if the camera were mounted on the TV; however, it is shortly revealed that the camera is located across the room from where Nicholas and the TV are located, not mounted on the TV itself.
When Nicholas gets off the truck in San Francisco, it's daytime. When he arrives at his house, it's nighttime. However, seeing as how he walked the distance from the middle of the city to his house, it would have taken him several hours to arrive at his house.
When Van Orton and 'Christine' leave from his office in separate taxis, Christine's cab stops just off-camera - the reflection of the brake lights from the cab can clearly be seen in the bumper of the remaining taxi.
The goof item below may give away important plot points.
Near the end of the movie, Nicholas, distraught over what he believed to be the death of his brother by his own hand, calmly strolls to the edge of the buildings roof and walks off. The problem with this scenario is that in order for the "game" to play itself out to completion, he had to leap from a very specific point on the rooftop. The camera shot from within the ceiling as he crashes through the glass shows that his downward path led through a very narrow space between the metal I-beams and other structures. A deviation of a mere few feet in any direction more than likely would have resulted in Nicholas' death. Since there were no erected barriers on the roof or gaming personnel guiding him to the exact spot for him to fall from in order for him to safely descend through the glass ceiling, there is no guarantee that he would have chosen that exact spot. It's inconsistent with all the precautions and preparations made by the gaming personnel for them to leave so much room for error.