Character mistake: In the opening cinematic (before you press start), the group hears a witch crying, and Bill and Zoey go to investigate. Louis and Francis stay outside to keep watch. When, in the dark, Bill and Zoey approach the witch, Zoey puts her flashlight on the witch and Bill immediately says, "lights off!" Now here is the confusion - Bill knows it's a witch, so shouldn't he know what they sound like and not enter the room in the first place?
Other mistake: In the final scene of Crash Course as the survivors are escaping in the armored vehicle, any zombie that is in the way of the rescue vehicle goes right through it.