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: A minor point but no mention is ever made of the pilot who deliberately crash-landed General Carnaby's plane at Oberhausen airfield. Presumably he would also have been taken to the castle for questioning but I suppose this would have further complicated the plot and be another person needing to escape.
Plot hole: The radio set used to communicate with headquarters in England was in fact a British low power VHF transceiver with a range of a couple of miles at best. It simply didn't have the capability to reach England.
Plot hole: How could Colonel Turner both be in London during the mission and in the pick-up plane? A Juncker can fly approx 220 km/h. It is approx. 1200 km from London to Southern Bavaria. That means that Colonel Turner would have had to leave London 5½ hours before the pick-up. The team does definitely not spend 5½ hours from the last time we see Colonel Turner in London until the pick-up.
Plot hole: When Smith and Schaffer are entering the castle via a rope Mary has lowered for them, Smith stops halfway up to look through a large window. Clearly visible through this window are the faces of at least two soldiers with others in the background. It is inconceivable that not one of them would notice: A) the rope suddenly dangling outside; B) Smith's solid frame as he stares in at them; C) Schaffer scrambling up the rope after Smith; or D) the rope bouncing around while Schaffer drags it in along with the attached backpack. (01:10:00)
Plot hole: In one scene, the heroes of the film (i.e. Burton, Eastwood and others) locked themselves up in the cable car control room within the castle. The pursuing Germans wasted valuable time trying to break down the heavy wooden door of the control room with axes. Why didn't the Germans use grenades or other explosives? They could have instantly blown open even the sturdiest wooden door.