Character mistake: The SS guard salutes Major Hochstetter with his palm out, in the British fashion. Firstly, German soldiers salute palm-down, secondly, by the Wehrmacht (and SS) military protocol, he should just click his heels and not salute at all when receiving an order.
Continuity mistake: When Hogan is talking with Lily Frankel before the double agent comes over, Hogan is lifting his beer. When the camera goes to close up, he's lifting it again. Also, in the long shot, the beer is down about three quarters of an inch from the rim. In the close up, the beer is nearly full.