I think it's one of 3...maybe ALL 3 of these, your "peeking", or your dropping your bow arm in order to view your shot, or yourunknowingly grippingyour bow as your excitement level increases with each step closer the deer get to within shooting distance.

Have you tried setting up a video camera and filmed yourself shooting?

Is your bow string smacking your jacket?

Are you sighted in with broadheads?

I have heard that those illumanocks havehelped people who can't seem to stop "peeking" because they can pick up the arrow flight without "peeking". Just a idea for you maybe.