Character mistake: In the courtyard of the castle there is an anti-aircraft gun. You could probably not find a worse place for a gun like that even if you tried (except maybe if you put it inside, in a windowless room). In the position it is placed it can only fire at targets directly above the castle. What you want to do is fire at targets before they reach the castle. It would be better if they placed it on the roof, or even near the village below.
Character mistake: The adjutant who wakens Major Wilhelm Wilner to tell him he has a phone call from the Schloss Adler has no breast eagle on his tunic. (01:27:40)
Character mistake: Before entering the tavern,Smith tells the team to meet outside in a 1/2 hour. When they are sitting at the table just before capture, he says he gave orders for nobody to leave.
Character mistake: Lt Schaffer (Clint Eastwood) is wearing his War Merit Cross With Swords badge upside down on his tunic. It's supposed to be worn with the sword handles at the bottom but his are at the top. Best view of this is when he is leaning against the bar of the tavern at 00:36:03 and has just watched Major Smith get slapped by Heidi. (00:36:03)
Answer: When the guard comes in, Burton explains what's going on. Also he is dressed as a German officer so his explanation and actions are plausible.