In the gun battle at the final, the house is besieged during the night. Hovewer, when Jasper, Gina and Dr. Polda escape towards the plane, there is clearly daylight (the editing is parallel, so there should have been the same time of day)
The scientist Katerin Lodor tell to Jesper that the italians are helping the nazis with the atomic project.
In real history italians scientists as the vip Enrico Fermi where helping the U.S. project not the nazi's one.
When Gary Cooper's character travels to Italy, he impersonates a German scientist from Berlin. But when he speaks German, his accent is so abysmal that It would have immediately blown his cover.
Establishing footage of Switzerland goes back to about 1920, based on the vintage women's fashions and automobiles briefly seen, even though it's supposed to be contemporary mid 1940's WWII era.