Blade won't turn if blade stud tight as I would normally have it. Any looser though it won't cut and the blade stops once it makes contact with the wood but the motor is still running. I assume I should be able to spin the blade by hand when the unit is in-plugged but not the case when I tighten the blade stud with the slide wrench. I can spin it when looser. Any thoughts as to what the issue could be? Thank-you in advance for any assistance.