The gun Frank takes from Jesse's truck is an old-fashioned six shooter, yet he fires off at least 20 rounds without reloading during the shootout at the gas station.
When Karen goes back the final time, she stops just before the sign, completely off the road. When she gets out of the car, the tail end is hanging over the road.
During the first iteration of Karen reaching the Accelerator Project door she is still wearing her white top tied around her waist. In the security camera footage showing her from above, she is only wearing the black jumpsuit (which is from the second time she comes to the site). The next cut shows her running back to Brian's truck wearing the white top tied around her waist.
When Frank tells the 'belt buckle' joke the punch line changes.
Karen is wearing a slightly different top as she climbs the fence to the one she wears before and after (straps are wider).
When Frank is pulled over the Trooper asks for "license and registration". In Texas registration is displayed on the windshield on the driver's side. In Texas law enforcement officers ask for license and proof of insurance during a traffic stop.
Frank racks his slide-action shotgun repeatedly without having fired it. Every one after the first he would be ejecting live rounds.
The movie was definitely not shot in West Texas because of the presence of Joshua Trees in almost every background. They are not found in Texas, only California, Nevada, Utah, and Arizona.
Near the ending with the car chase in the desert with the station wagon, the police car loses a hubcap. Subsequent shots show the police car with all 4 hubcaps intact and then after that shot one hubcap missing again.
After the Gold 1970 Cadillac Sedan De Ville flips over in the desert there are scenes of a BLACK Cadillac burning.
A stage light and the camera operator are reflected on the side of Frank's car when he reverses to pick up Karen.
Multiple indications such as Joshua trees and mountains show that filming took place in the southern California desert instead of Texas.