Other mistake: The 'Fire Drill' will be a wet business for Lieutenant Werner - the right side window on the car is open. At least you see a horizontal line almost halfway down on his side window. You see it when they meet the Bosun's Mate (time code 1). When they meet the men at their Fire Drill, (time code 2) it even looks as if Lt. Werner opens his window. (00:02:35 - 00:03:15)
Other mistake: During the heavy storm which lasts for 3 weeks, you can see clear blue sky above the U-Boat.
Other mistake: Prochnow drives to the boatyard in the opening scene - the drunken crew at the side of the road initiates him by pissing on the car as it passes. His passenger had just rolled down his window, when he saw the crew, but there is no evidence that he rolled it up before passing the crew. (00:04:55)