I think, pretty sure that connector was so close to the frame that expansion heat, or rain, let it jump the Gap and short against the frame. When I removed and reinstalled it was even closer, and when it loosened it made solid contact and blew fuse. Even all the way on correctly I doubt there's even a quarter inch clearance. Really bad design, no idea why the female spade rubber insulator is open topped and a separate piece. Cheaper, I guess, but I've seen plenty with a solid rubber coating. If the connector isn't 100% tight, the metal top is proud of the insulator, and can short to anything it touches.
Off to celebrate with a beer with Guzzi Dan, rain tomorrow, maybe a long enough test ride Wednesday to see if that was the whole problem. Started and ran fine.