has the gb been worked on recently?
if it has, it may be to tightly shimmed.
the reason you are getting that mark on the heat shrink tube on your positive conector is because your motor plate is pushing directly onto it you need to gently bend it away from the center towards the out side. that is why your motor adjusting isnt makeing a difference, the motor adjustment screw isnt doing anything cause the motor isnt sitting on it. that is also why, in yur vid, the motor plate doesnt look like its going all the way into the grip.
if you live in the west valley you can come over to my house and i can take a look at it and help you better that way. if you are in the east valley go to gearbox and they can give you a hand.