Revealing mistake: This film has the old movie trait of Nazis having German accents rather than actually speaking in German, which is fair enough as they take up the majority of the screen time. However, not everyone adheres to this rule and there are many characters, minor and major who slip in and out of accents, and many never have them at all.
Revealing mistake: Ms. Grey's door is kicked open by the US colonel. A split second before he kicks it, though, the door mysteriously becomes unlatched from the inside. I guess this is so the actor wouldn't hurt his leg.