Audio problem: At the end of the elf concert, when Mrs. Claus walks right out right after Santa does, we hear the sound effect of a door slam before she even closes the door. (00:13:40)
Audio problem: When Kevin plays the tape of his Uncle Frank singing in the shower, it starts with "We know a guy that can really do the cool jerk" twice. Yet, when he first tapes his Uncle, he doesn't start the recording until after that has been sung. The recording also sounds very clear. When he tapes him the door is closed, but the tape sounds the same throughout. Also, when his Uncle says he's gonna "slap him silly" Kevin shuts the door behind him and you can hear it shut. On the tape there is no sound of the door shutting.
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 Scott is making a distraction, he says, "Well, this show stinks." But his mouth is saying, "Well, this show sucks." Done in order to keep the G rating, I presume.
Audio problem: When Kevin is going through Buzz's private things he finds a picture of his girlfriend. Sickened by her appearance, he smashes the picture. But the smashing sound starts before he hits it. (00:22:05)
Audio problem: When Abby, an elf, is about to tell Santa that Charlie is on the naughty list, she says something about 'Brazilian cocoa beans'. As this line is heard, you can see that her mouth is moving completely differently from the words we hear.
Audio problem: When Willy Jones and Moly are slapping each other in Moly's donut shop, Moly says "hey buddy" but his lips don't move.
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.
Audio problem: Just after Hans addresses McClane by his name over the radio, we can hear Powell say, "Better get ahold of someone at dispatch," but his mouth movements don't match what we hear. (01:18:50)
Audio problem: You can tell that Tia is lip syncing in the final song ("Oh holy night") more so on the last few lines she closes her mouth before the song ends.
Audio problem: When Ernest pushes the cart with the passenger on it, he accidentally goes into the conveyor, Ernest says, "Have a nice day." When Ernest says this, his lips don't move when he says it.