Before I disclose the gaping hole, I need to address an obvious objection to my endeavour. Surely to worry about logic in a merry seasonal fantasy misses the point? However, I've always argued that, while fantasy can clearly change whatever rules it likes, once the nature of the fantasy world is established, it should be logically consistent. This is why I don't have trouble with vampires and werwolves and slayers and magic in Buffy the Vampire Slayer, because that is the part of the rules of the world. But I do have a bit of an issue when a hobbyist manages to come up with a robot that is all but indistinguishable from a human being - because the technology in Buffy is the technology of our world, and that just isn't possible.
So back to the Santa flaws. (It's just one flaw really, but 'Santa flaws' sounds much better.) The article I was reading (sadly I've lost the link) pointed out that, in these films, Santa Claus is real and goes around the world delivering (at least one) present(s) to good children on Christmas Eve. That's fine. That's part of the premise of the movie. But bearing in mind these presents magically turn up in everyone's house each Christmas morning, why would anyone not believe in Santa? That just doesn't make sense. And without logic, the magic falls apart.
Ho, ho, no.