Continuity mistake: When the Bellas just got told that they are not allowed to compete any more they walk outside and Beca gets a call. When the camera is zoomed in on her you see her calling and moving a lot. When the camera is focusing on the other Bellas she is standing completely still in the background. When the camera is back on Beca she is moving again. (00:12:50)
Continuity mistake: Before the Bellas' second performance, one of the girls is getting her natural hair braided. When the performance begins, they are completely different braids with added extensions.
Revealing mistake: When the crew does their first choreography practice with the new Bella, in the top left corner you see Amy and another Bella holding another girl in the air. You can see she's standing on a table, basically supporting herself.