The bow of the ship that carries Von Werra to Canada is seen in close-up travelling symbolically right to left across the screen. Unfortunately, the original stock footage was of a bow travelling left to right and the editor just stuck a piece in, reversed. The numbers are mirrored.
As stated early in the film Franz Von Werra had a straight forefinger on his right hand. However, at various stages during the film, Hardy Kruger had apparently forgotten this, as he continuously bends that finger.
When Von Werra crash lands, the cockpit canopy hood on the BF-109 mock-up is hinged on the port side and he exits on the starboard side. All actual BF-109's were the opposite; the cockpit canopy hood being hinged on the starboard side with the pilot entering/exiting on the port side.
When he first reaches the snow-covered frozen river, there's already some footprints in the snow.
On the train travelling through Canada you can see that all the windows are frozen over but when it stops at a station an exterior shot shows Hardy Kruger's is clear so that he can see out.
When Von Werra ducks beside the ice-covered road to avoid a car, the car is an early 1950's Chrysler product, even though the story is set in the winter of 1940-41.
Whilst being driven to Station HQ at Hucknall, he passes two aircraft on the flight line. The first is a DHC-1 Chipmunk which first flew in 1949, nine years after the film is set and four years after the end of WWII.
At one point, as cover, Von Werra says he is part of the Royal Netherlands Air Force. While this would be correct for 1957 (the year the film was released), in 1941, it would be known as the Dutch Army Aviation Brigade.
Note: von Werra is in the German air force (Luftwaffe) and has escaped from a PoW camp, and is in a British shop still dressed in his flight suit but with the insignias etc hidden. He is then approached by a suspicious police officer (with the people in the shop listening) and as a bluff makes the false claim about being a Dutch pilot, and it works. Not being Dutch he simply might not have known the correct Dutch terms to use, but neither might any of those present in order to dispute it - since none of them are Dutch either.
Note: von Werra is in the German air force (Luftwaffe) and has escaped from a PoW camp, and is in a British shop still dressed in his flight suit but with the insignias etc hidden. He is then approached by a suspicious police officer (with the people in the shop listening) and as a bluff makes the false claim about being a Dutch pilot, and it works. Not being Dutch he simply might not have known the correct Dutch terms to use, but neither might any of those present in order to dispute it - since none of them are Dutch either.