Other mistake: The camera focus is on Lt. Weaver during the German armor attack, but off to his left (barely in the scene) Sgt. Duquesne drops a live rifle grenade as he is foolishly flipping them in the air before securing them to his rifle and firing them at the Germans.
Other mistake: When Jimmy Stewart talks to George Kennedy about the taking of his son as prisoner. Right after they look at the map. Look over the shoulder of Kennedy in next few frames. You can see a white vehicle move across the horizon under the mountains. Looks like a white van or truck. With a HD TV, you can even see the dust trail as the vehicle moves left across screen.
Other mistake: After being torpedoed, John Wayne orders Burke to radio Pearl Harbor. Burke asks "And break radio silence?" to which Wayne sarcastically replies "don't you think the Japanese know our position?" Actually, a submerged WWII sub could not transmit (radio) without surfacing. Having run up on the submerged sub by chance, only the sub knew their position at that moment. Breaking radio silence did in fact give their position away to the Japanese command.
Suggested correction: A W WII submarine usually surfaced to fire a torpedo thus raising a radio antenna above the water, allowing broadcasting.
Surface torpedo attacks occurred only at night less they give away their position in daylight.
Other mistake: When Ryan arrives at the camp he observes a funeral taking place yet when he goes to meet the camp Commandant he asks what they are celebrating outside.
Suggested correction: I would agree that a funeral is not really an occasion for "celebration." The British regiment are holding a funeral for one of their dead officers: they are speaking English, and since Colonel Ryan is a US soldier, he can fully understand what they are saying, and he should know what is going on. He has worked out that a funeral service is in progress, but, having only just arrived at the POW camp, he will not know all the details of what is going on, and might be interested to know more. It might be insensitive to ask one of the British soldiers, so he decides to ask one of the Italian guards instead. Now, Colonel Ryan's history previous to the start of the film is not described, but he must have experienced some harrowing events in his military career, and this has probably left him feeling cynical and bitter, so he is probably using sarcasm. After all, Colonel Ryan is rather sarcastic throughout the rest of the film, too.
Other mistake: In various scenes during the movie, a stretcher with the dead body of Stevens is being carried around the prison. There is obviously nothing on the stretcher but a blanket. There is no body, whether actor, dummy or other, just a blanket over an empty stretcher.
Other mistake: When Knut and Rolf leave Anna in the car on their way to plant the explosives on the ferry, they instruct her to wait no more than 2 hours for them. Once on the ferry, the earliest time seen on the alarm clocks is about 01:10 so we can assume that Knut and Rolf left Anna sometime before 01:00. When they return to the car after the explosives have been planted, you get a brief glimpse of Anna's watch which shows the time as 03:35; a full 2 hours 25 minutes after the 01:10 we saw on the clock yet Anna states that there are 9 minutes left. (01:44:06 - 01:53:57)