Continuity mistake: When we see Christmas Flint with her dad and Miss Rayleen for the first time, she's watching them bicker, her chin perched on the back of her hand. Which hand, though? It's her left hand for the greater part of the scene, but in the shot when Jim Gaffigan is saying "I got to find my pants. You move my pants?" it's the right one. (00:05:00)
Continuity mistake: The protagonists escaped from captivity and managed to return to Harry's palace. Luka decides to leave to go look for his mother. Harry seems to send him off, and he is standing in the middle of the stairs, about 4 steps below the guard. Harry at this point is in close-up; the guard is not visible, and at the next cut somehow Harry shoves him off as if he were standing directly behind him. (00:16:00)
Continuity mistake: When Aunt Sarah arrives, she dumps her luggage in the hands of Jim and then passes him to his right, leaving him between herself and the door. In the reverse shot, Jim is on the opposite side. (00:29:15)
Continuity mistake: In the prologue, the Nazis storm the Bresson residence. The elder Professor Bresson is sitting at his desk, back turned to them. There's an open fountain pen next to him, right by a paper sheet, but when Bresson answers rather defiantly to the bad guys, the paper sheet suddenly has disappeared. (00:02:15)
Continuity mistake: When Hodaka first fires his gun whilst being threatened by the man, the shell casing lands on the ground beside him, right next to his head. A couple seconds later, when Hina goes to help him up so they can run off together, the shell casing has vanished from the ground. (00:22:06)
Continuity mistake: When Santa tells Noelle he's anxious about inheriting his dad's role, the position of his arms is inconsistent between front and side shots.
Other mistake: Jodie mentions wearing shoe size 13 more than once in the movie yet look closely and those are only size 10 shoes.
Deliberate mistake: The prisoners in the dark dungeon would not be able to read the letter (to Miss Dudley from Jason Flemyng that the carrier pigeon had) or see such a clear reflection by pouring water on the stone floor and holding the letter (written backwards) by the water. The room was suddenly lighter when doing so, but it wasn't clear where the light was coming from. Also, sunlight coming through the small window would not beam straight down along the wall. (00:07:23)
Continuity mistake: The clocks are not coordinated, affecting the time frame. Josh and Jen are decorating the Christmas tree at 8:08 PM. Josh goes to his room, "past his bedtime." Josh writes his list for Santa. At 7:15, Josh hears a car drive up, so he looks out the window. Dad meets mom in the driveway and says, "It's almost midnight." (00:05:29 - 00:07:58)
Plot hole: SPOILER ALERT! During the final fight, Joey kills Frank and she reverts back to human form. Abigail tells her she's fine, because Frank was the one who turned her. However, when Frank kills Lambert he does not revert back to human form, even though Lambert was the one who turned him.
Suggested correction: Because it was too late for Frank, who had already turned, Joey hadn't.
If that were the case, then why would Abigail bother explaining to Joey why she reverted back to human form?