Continuity mistake: Simkins finds the girl in his wardrobe in his room on the train. There are two jackets hanging up in the right hand side of the wardrobe - when he opens the wardrobe door again immediately the girl has gone but the jackets are still there. Harold Crump then enters Simkins' room - the wardrobe door is still open with no jackets visible, but when Simkins closes the wardrobe door there is only one jacket hanging up in there.
Other mistake: When our heroes are on the conveyor belt in the rock-processing plant, none of the rocks are larger than two feet in size - especially having gone past a set of spinning saw blades - and yet they get sprayed by two steam nozzles, the highest of which is about six feet in the air, and the lowest is about four feet in the air. Clearly neither of these nozzles would have any practical use.