Plot hole: Why do all the Germans abandon the cable car control room after the alarm has been sounded? If the cable car is critical for access to the castle then you would expect a hard core of SS troops to remain behind to control access and protect the machinery in the event of an attack. (01:42:55)
Plot hole: The movie is based on one huge plot hole: if it wasn't for the "professional" hitman's sloppy work, Bullitt and his team wouldn't have been needed for much. The hitman enters the hotel room, wounds the policeman, then shoots the target with one shotgun blast to his upper left shoulder area. Any hitman worth his fee knows that this is not likely to be an immediately fatal wound. The hitman had a pump shotgun and should have finished the job right then and there. Surely he had more than two shells. Instead, he sees the target is slumped unconscious, then leaves the hotel room without checking to see that his victim really is dead. Nothing seems to be immediately threatening the hit team, though. The hitman spends the rest of his life trying to finish his job and pays the ultimate price for being lazy.
Plot hole: Patrick McGoohan shoots the marine captain thinking him to be the traitor, thus, McGoohan believes, stopping the marine killing Ernest Borgnine. But shortly afterwards McGoohan comes out of the hut and addresses Borgnine sarcastically as 'Comrade'. How did he know he was the real traitor? Nothing has yet happened that should cause him to see this truth.
Plot hole: Wouldn't Taylor have suspected he was still on Earth, seeing as all the apes were speaking English?
Plot hole: On her first night alone on the McBain farm, Jill hears someone playing a harmonica out there in the dark. She blows out a candle (but there is still plenty of light in the room), grabs a gun, positions herself at the brightly lit window, and shoots when the sees tha harmonica player lighting a match. This behavior is way too foolish for a women depicted as street-smart as Jill. (00:55:30)