You don't have to boresight to see if it is the zero stop. See how much adjustment you have 'up', ABOVE where you say it is bottomed out. It takes less time to check, than it did to reply. Did you read the manual about the stop? If it was adjusted all the way to the bottom as you say, you've got a defective scope. Best not even mess with it anymore. Return it or toss it. Or take the 5 whole minutes it would take to research the problem, and fix it. And please, quit 'thinking'. Use those faculties to actually assess the situation instead.