Continuity mistake: The vampire who gets tossed into the grinder mysteriously reappears in the final showdown. You see him twice while the head vampire is fighting with Eben.
Revealing mistake: In the scene Josh Hartnet's character dumps the vampire into the grinder, and gets beat up by the one who turned into a vampire, in the close-up shot of his face where he is bleeding, look at his nose. The patch make up used for supposed ripped flesh is visible. It's colored orange and is rather obvious.