Audio problem: When the elves are marching around, listen to the footstep sounds and watch their feet. A lot of times the noise and movements don't match. This is especially apparent when the five elves who have been taking wish calls go to the transporter.
Audio problem: When the carolers come to sing for the Kranks, it is professional-quality singing. Then the neighbors join and you can hear that more people are singing, and the quality of the singing is realistically worse(the neighbors can't sing well.) After a few shots of the carolers AND the neighbors singing, the sound goes back to just the carolers singing, though you still see the neighbors singing on screen.