I think that you might have a tensioning problem. Perhaps the spring is stretched somewhat and the wider belt made the difference. I would also check the tensioning pulley to make sure the lever it is mounted to moves like warm butter. The other possibility could be a glazed drive belt and some glazing on the driven pulley. Just because it's working OK now is no reason to not get to the heart of why it wasn't working with the old belt. :thumbsup: