Continuity mistake: When BB-8 hears the creature come up from the sand behind him, he stops. Just before he turns around the orange rectangles on the left side of his face to being almost all uniform in shape and size, to now having two big ones on the ends and two small ones in the middle. (00:00:30)
Revealing mistake: When Andi walks into the library (this is not Andi's dream) it cuts to the librarian sitting at her desk and we can see the shot is flipped - note the bookcase and the librarian's buttons. (00:10:40)