Factual error: When Lt. Dunbar is being interrogated in the Commandant's office you can see a map on the far wall. It is a map of Germany dictated by the Treaty of Versailles which ended World War I because it shows E. Prussia separated from Germany and does not include the annexation of Austria and Czechoslovakia. These annexations were completed before the start of World War II in '39 and certainly before late '44, early '45 when the film took place. It is highly unlikely any German officer would have this map displayed not only because it's inaccurate but because it displayed the territorial losses brought on by the humiliating defeat of World War I.
Factual error: At the start when Manfriedi and Johnson are ambushed outside the wire, check out the "German" crew served machine gun. It is actually a U.S. mod. 1919 air cooled 30 Cal. Browning. Germans used MG 34 and later MG 42s. But for a rear area POW camp they would surely use 34s to save the newer faster 42s for the front.