Continuity mistake: Everyone is having dinner at Lady Catherine's house. Watch the candles in front of her. In the close-up shot of her face, every candle is standing up straight. In another shot, further away, the second candle from our left (Lady Catherine's right) leans towards the left side of the screen.
Continuity mistake: The first time we see Georgiana playing the piano she is in a room with a harp and her back is reflected in a mirror. We can see it is the music room. The second time Georgiana is playing the piano, it is in the room that leads into the music room boasting a long red couch as the backdrop, The piano forte seems to move about the castle as it sees fit.
Continuity mistake: Kitty has just spotted Mr. Bingley returning to Longbourn from the window. She is seen through the glass wearing two bangles, spaced several inches apart, on her left lower arm. Cut to the immediate next shot from inside the room and the two bangles are now on top of each other on her wrist.