When the American is watching the alien at the back of the pub, his rifle changes position depending on whether the camera is in front of him or at the back. Sometimes the butt in down, then it is up.
When Jeff Nolan first arrives at the village he takes out what appears to be a bolt action Enfield P14 / M17 rifle, later in the film this turns into a semi automatic 30-06 Garand rifle.
The American is a pilot but uses Over and Out on the radio. Over means I have finished but am waiting your reply. Out means I have finished transmitting, I expect no reply. The 2 should never be used together.
When the couple is shown in their wrecked car (approximately 5 minutes into the film), the man's eyelid moves.
At around 5:40 into the movie viewers can can see the woman in the crashed car breathing ever so slightly.
At the very end of the film when the airplane takes off, cars can be seen being driven along a road alongside the airfield (directly opposite the camera). Since most people are assumed to be dead, it would be unlikely to see cars being driven on the road.
If they 'aliens' are robots, why do they need space suits.
The dial on the petrol pump does not move when Taggart fills the MG with petrol.
When Jeff walks over to the car crashed against the pole and checks Violet and Edgar Otis, he concludes up close that they're dead but the story plot has them as unconscious. A test pilot should have more experience with checking a body, from combat experience. It would have made more sense if he hadn't bothered to check them out closely and just assumed from afar that they were dead.
At the end of the movie, they take-off in a jet airliner but it sounds like a propeller driven aircraft.
Jeff Nolan (Willard Parker) says he is a pilot and was flying and that's why he survived the gas attack, yet during the opening scenes an aircraft crashes because the pilot is slumped over the controls.
It's never overtly explained why Quinn Taggart insists that Peggy Hatton pretend to be his wife other than his telling her that it would be "safer". His subsequent insistence to take her hostage seems to imply that he intended all along to force her to be his mate, going forward.
When the young couple arrives in their car. Jeff walks up to the passenger door to speak to them and the boom mic can be clearly seen in the windscreen/windshield.
When searching for guns, Taggart announces that he has found "automatics" but all of the shown guns are revolvers.