The night when Duncan Marsh first appears in the film, he has a couple days' beard growth. The next morning he wakes up in a drain pipe clean-shaven. Later the same day, as he looks down at the roadblock, his stubble has returned.
Sometimes the Werewolf has fur on his neck, and sometimes it doesn't.
Just as the werewolf grabs the meat bait from the rock and right before stepping in the trap, the shadow of a crew member passes over the werewolf's right side from behind the camera, on the left of the screen.
When Nurse Amy says, "There is a word for what you're saying, Jack." Sheriff Jack responds, "Yeah, I went to school, Amy." They don't teach about werewolves in school. Unless he is talking about learning about werewolves in "Little Red Riding Hood" in kindergarten.