After their first rehearsal, Janey tells Lyn how she was with Jeff for over an hour. This is impossible since they are clearly only in the room for no more than 5 minutes - the same song is playing the whole time through that scene, and is still playing when Jeff leaves.
About an hour into the film there's a montage of Jeff and Janey practicing in the park. In one sequence Maggie is sitting in a tree looking on as Jeff jumps off of it. Jeff lands and turns to look at her. The shot of her reaction was flipped, as the text on the Pepsi can she's holding is backwards, and the tree she's sitting on is now on her left (screen right) instead of her right (screen left). This was obviously done to match the direction of the shot of Jeff looking at her.