Revealing mistake: When the police car crashes through the grating that was dropped down in front of it at the end of the tunnel, the occupants are dummies - they just bounce about in the same upright position whilst the car drives into the river.
Revealing mistake: When Bond throws a Blofeld henchman off a cliff near Piz Gloria in the Alps, you can see that it is a dummy, as its arm swings round and wraps around the whole dummy.
Revealing mistake: Technical Glitch: In the opening scene before the opening credits. The British are being run out of one of the last remaining fields in France. The Sergeant is burning the "lame ducks" when German planes attack. A German plane attacks almost directly toward the camera, you hear machine gun noises but no effects. Next a plane attacks from right to left, you hear machine gun noises and see the effects indicating the bullets striking the target. After the second plane has gone you see the effects of the first planes attack.
Revealing mistake: When the Remagen bridge is bombed, it is obvious that the bomber planes shown have been taken from several shots (possibly also from an earlier film) and the shots were superimposed. Also, the bombers appear transparent, and the background sky's color is unnaturally strong, too.
Revealing mistake: Near the end of the movie, the Bunch are relaxing and passing around a bottle of whiskey. While the actors could not be expected to drink real alcohol, it's too bad the prop guy could not have mixed up some less foamy instant tea, typically used as a substitute in these scenes.
Revealing mistake: Captain Beckman is in the tower shooting at a small German plane that is attacking the castle. He is told to aim for the engine but when he does and shoots it down its not the engine that smokes, its both the wheels that are smoking from some very obvious smoke tubes attached to the fixed landing gear.