Continuity mistake: When Bradley and Jennifer arrive at the dance competition they end up holding hands. As they make their way upstairs to register, Bradley is on the left of the picture, but as the scene cuts (in real time) from them starting up the stairs to getting to the top, they have switched sides. Then, very briefly, when Jennifer goes to use the restroom, they have switched back again.
Continuity mistake: In a group scene with Bradley Cooper's family, Jennifer Lawrence arrives and has a beer. While she's talking the camera pans the group. At one point Bradley Cooper responds. While the camera is still on Lawrence, you can see Cooper at the left of the screen. Although talking, his jaw isn't moving.