Factual error: Just like in the previous movie, Herzog is referred to as "colonel", in particular in the WWII museum where Martin reads about his history. But both in the museum's picture of him, and throughout the movie, Herzog is wearing the uniform of a SS Standartenführer. To hold a title of Oberst (colonel), he would have been a member of the Wehrmacht, regular army, not SS.
Revealing mistake: As Glenn, Blake and Monica are being surrounded by zombies, as Monica asks "Fucking hell, how many more of these are there?", in the background you can see a zombie sitting astride his victim, flailing away with a hammer or hatchet. It is obvious that he is just swinging his arm back and forth, without connecting with anything. It looks as if he is dusting, not slaying someone.