Revealing mistake: The first shot of the train the view is normal. Then after Lebeau starts in reverse you can see the smoke trail going in the wrong direction. The final shot shows the train moving in reverse, but notice the smoke trail is going to the rear of the train instead of the front as it should be, since it's moving in reverse. (00:15:05 - 00:22:25)
Plot hole: In his German uniform, Col. Hogan wears a number of decorations, among them the Iron Cross first and second class. When did he earn those if he has just been drafted for a suicide mission? After all he was not posing as a Wehrmacht soldier for a change but wore the uniform "officially". (00:17:00)
Answer: It's a solitary cell. Steve McQueen, star of 'The Great Escape' is known as the 'Cooler King'.