Continuity mistake: Throughout the movie, fire axes seem to be the weapons of choice. Only two fire axes are used, but they appear recurrently. In the very first use, the protagonists grab fire axes to butcher the monster called Beverly. Blood and gore go everywhere; yet, the axes emerge from this bloodbath with no blood or gore on the handles - they're virtually pristine moments later. The axes are used again and again, right up to the ending, and blood comes and goes from the axe handles seemingly at random.
Revealing mistake: When Gabby and Fin are hanging off the building in Las Vegas, you can see that Gabby isn't holding on to anything in some close-up shots. (00:11:47)
Factual error: A bullhorn can be heard in the background off-screen during a battle with the zombies, even though the movie takes place during Victorian times. (01:19:30)
Continuity mistake: The cursed necklace is shown emitting its evil fumes on the white paper of the letter, but the letter itself is perfectly 90° with the envelope, or at a different angle. (00:06:20)
Revealing mistake: Right after the little girl sprays the monster with bug spray, you can see the costume of the monster, it's wearing a black cap. (01:19:00)