Character mistake: Hicox salutes General Fenech, who returns the salute. But Fenech is bareheaded and therefore under British military protocol cannot salute. He would instead acknowledge the salute with a nod.
Character mistake: The narrator says that Hugo Stiglitz killed 13 Gestapo Officers. However, the newspaper's pictures and the text below them show that some of the officers were Wehrmacht officers.
Character mistake: Hicox claims to be from around Piz Bün to explain his strange accent. However, Piz Bün isn't even in Germany and nobody around there spoke German at all. Yet nobody reacts. It's very weird that Hellström, being a German officer, would not know the borders of his own country.
Suggested correction: A lot of Germans come from Austria, or lived in Austria. To the Nazis, Austria is part of Germany. Hitler was born in Austria too.
Character mistake: Hicox uses the word "momentarily" in the American sense of "in a moment". In British English it means only "for a moment". An educated Englishman in the 1940s would never have used the word in the American sense.