Factual error: In the famous tugboat scene, Fannie rides out on a New York Central tugboat painted jade green - a color which wasn't instituted on the boats until the early 1960s. To be accurate, the tugboat would have to have been painted red with a black stack and the New York Central logo.
Continuity mistake: When Gregor and Willie are attacked by the German convoy, they pick up two discarded StG 44s, but in th next scene they are firing AK-47s which had not yet been invented. After the battle, they are again carrying StG 44s.