After the trio stops to disconnect their stuck car horn, further down the road they experience a tire blow-out. As the car comes to a stop, the car horn can be briefly heard.
When the rifle is used to shoot the can off the rock, it comes back to the front of the rock. It should have gone to the back.
When Frank Lovejoy shoots the can from Edmund O'Brien's right hand with his rifle, the next scene shows the rifle with the hammer cocked which it would not be if he just fired the rifle. The rifle is a pump .22, not a semi-automatic.
When the Mexican police car first appears (the Nash Ambassador), at around 39 minutes, the door reads "POLÍCIA DEL D.F.". Later, at approximately 55 minutes, when the officer stops to check the victims' car, the sign on the door reads only "POLÍCIA".
The Chocolate Mountains are in California not Arizona. However, it's clear that the two are trying to mislead Emmett as much as possible with regard to where any searches might be conducted.
Late in the film when a helicopter flies over, the point of view shot from the helicopter is not only clearly not the same location the actors are in (it is much more desolate), but it also has camels in it - which would be very unusual in the Mexican desert.
When the men remove the tire from the car, it is fully inflated as the profile of the tread appears to be convex. The tread of a flat tire would appear straight across or concave.
After Emmett Myers and Roy Collins switch clothes Myers is seen wearing a khaki colored baseball cap in addition to the shirt, jacket and trousers previously worn by Roy Collins. Prior to the clothing switch Collins was not wearing a cap of any kind.
In the scene where two policemen interrogate the driver of a vehicle, the lettering on the door of the police car clearly says "Policia del DF", in other words, "Police of the Distrito Federal", that is, Mexico City, which is located in south-central Mexico. But the fugitive and his hostages are supposed to be in Baja California, a long way away from Mexico City. And in the matter of an international fugitive, it would most likely be the Federal Police (los federales), the national police force, rather than municipal police, looking for the fugitive.