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.
Continuity mistake: Santa is holding the snowglobe as Jack Frost enters the scene. As Santa bends down to speak with Lucy, his hands are empty and Lucy is holding the snow globe and she proceeds to give it to Santa.
Continuity mistake: The second time Jack and Santa fall from the sky and are laying in the snow outside the townhouse, it cuts to the scene from the The Santa Clause where Scott Calvin first puts on the coat. However, in the original movie, Scott doesn't put the coat on until after he and Charlie have left the townhouse in the sleigh and are on the roof of the first house in which Scott goes down the chimney.