Character mistake: David Niven and his father are playing chess, and to checkmate his father, David Niven makes two moves, which you absolutely can not do - the only time you can move 2 pieces is when you move your castle and the king at the same time (castling), but you can't do that when you are in check.
Wuthering Heights (1939)
1 character mistake
Directed by: William Wyler
Starring: Laurence Olivier, David Niven, Flora Robson, Merle Oberon
Continuity mistake: When she enters the room and then turns around, Cathy's muff disappears between angles.
Heathcliff: Why are your eyes always empty? Like Linton's eyes.
Isabella: They're not empty, if you'd only look deeper. Look at me. I'm pretty. I'm a woman and I love you. You're all of life to me. Let me be a single breath of it for you.