Audio problem: When Penny and Johnny are teaching Baby their dance routine, Penny puts on a record. Look closely and you can see that Penny moves the arm to place it on the record, then she takes it away, even though the music is still playing. Even if it's a directorial device for us to hear different music than they do, it's still a mistake because she's not actually playing the record, meaning there isn't any music for them to dance to. (00:36:35)
Audio problem: During the "Hula Hana" scene, you can tell the little girl with the ukelele is only mimicking playing. A chord is heard being played in a staccato fashion, but the girl is merely rubbing her thumb against the body, and maybe striking the lowest string, while not fretting any of the strings with her left hand. Playing staccato on open strings would require you to use one of your hands to stop the open strings from ringing.