(at around 23 mins) After Jack Belicec cuts his hand, he and Dr. Bennell are talking next to the pool table. Dr. Bennell states that Becky's cousin (Wilma Lentz) thinks her "uncle and her aunt are not her uncle and her aunt". However Wilma's suspicion only concerned her uncle Ira. Her aunt was never mentioned.
(at around 31 mins) When Miles is carrying the sleeping Becky from her house to his car, her right arm is hanging limp on the way down the stairs and her left arm is holding Miles. But in the next shot at the front door her body position is changed, with her right arm around Miles shoulder and her left arm hanging limp.
(at around 1h 4 mins) At one point in the movie, Miles is knocked to the ground, and his hair gets visibly mussed up. Cut to the next scene where he stands up and his hair is neatly combed.
(at around 3 mins) In the beginning, when Miles is picked up by his nurse at the train station and she opens the car's back door for his suitcase you can see the back seat upholstery is a very wide tuck & roll. A few moments later as they are riding in the car you see it is a very tight tuck.
(at around 1h 10 mins) The water stains on the planks in the mine are inconsistent.
The opening credits say "Produced in Superscope." This is not true. It was produced (i.e. filmed) spherically in the wide-screen ratio of 1.85:1, then cropped to 2:1 and printed anamorphically in Superscope, despite the protests of director Don Siegel.
(at around 1h 10 mins) As the posse runs through Bronson Cave, after the policeman stops on the planks, says his lines, and then runs ahead, look closely for the man in the white shirt: it looks like he fell down onto the planks before the shot ended.
(at around 48 mins) The gas attendant took the keys out of the ignition to open the trunk to place the pods. After leaving, Miles stops the car, takes out the keys and opens the trunk to burn the pods. But although the car has been turned off, there continues to be exhaust smoke exiting the pipe.
(at around 57 mins) When the three trucks pull up to the town square, a man directs people to "truck 1" and "truck 2" and "the third truck," but there's no markings to indicate which truck is which.
There are no exit doors on the side of the train Miles is walking from. Also, no passenger train would allow passengers to cross another set of tracks to get to the depot.
(at around 24 mins) When Miles takes Becky home after visiting the Belicecs, she turns on the lights as they enter the house. When Miles turns off the lights, they go out just before his hand reaches the switch.
(at around 1h 4 mins) After Miles and Becky disable Jack, Dr. Kauffman and the police officer, Miles says, "Our only hope is to make it to the highway." This line has been dubbed in, and doesn't entirely match his lip movements.
(at around 20 mins) When Dr. Bennell is shown the body on the pool table he never bothers to ask where it came from or why it is there. One would think that would be the first question.
(at around 37 mins) The morning after Dr. Bennell brings Becky to his house, she makes breakfast for him. She asks if he wants his eggs boiled for 2 minutes. Then they hear a noise which is the gasman in the basement, and talk to him. She then runs back exclaiming "They'll be hard-boiled!". But they've only been in the water for 34 seconds. What she then serves would essentially be raw eggs.
(at around 18 mins) When the host at the Sky Terrace serves martinis to Miles and Becky he pours Miles' drink neatly, but with Becky's he dribbles much of it out of the shaker onto the bar instead of her glass.
When Dr. Bennell gives Jimmy a pill and a cup of water in his office, he asks Jimmy to open his mouth and close his eyes but Jimmy closes his eyes before Dr. Bennell tells him to.
(at around 52 mins) When Becky Driscoll parks the car in the used-car lot, she hits the right side of the rear car bumper of the other car. You can hear the distinct sound of metal being crushed.