Audio problem: In the scene where Penny and Johnny are teaching Baby their dance routine you see Penny putting on a record, if you look closely you can see that Penny moves the arm to put the record on then right away you see her taking the arm away even though the music has started. 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 put the record on, meaning they've not got any music playing. (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.