Revealing mistake: When Lanser goes below deck frantically trying to find people and tell them to leave the ship, when he opens the door at end of the corridor, it's a bit too obvious that the hallway behind that door is nothing more then just a painting.
Other mistake: Lt. Mueller's German accent drifts in and out.
Revealing mistake: When Lanser drops the cup, you can quite see that he is drinking from an empty cup, since the steward never poured him any and yet he manages to get some of it on his suit.
