Revealing mistake: When the driver is taking Amanda to the airport at the end, all the dials on the car are at zero, so obviously the car is not moving at all.
Revealing mistake: You can see Buddy and Finch's stunt doubles in the ice skating scene. And when they are showing a close up of them you can tell that they are not really ice skating, but just doing the ice skating movement.
Revealing mistake: When Neil is teaching Yoga exercises to the elves a first close up shot of one of the elves (the Asian looking one) shows he doesn't have pointed ears like the rest in the group.