Revealing mistake: When the Marines are jogging through the training camp complex, singing "I don't know but I've been told..." you can see the British road junction markings on the tarmac underneath them. There is little evidence to suggest that there was any attempt to disguise or remove them.
Revealing mistake: When Jim is riding the bicycle through the empty hospital, the "Frigidaires" begin falling through the roof. One bursts open, dropping its contents onto the floor. Something from inside must have landed on the camera because you can see it jerk suddenly.