This is a long post and beyond my experience but in case it is of any relevance it is possible for unusual problems to arise because of corroded or bad battery leads or connections at battery. Also have had some strange things happen from battery that had failed (even though battery seemed fine and had been charged). Thought I also remember it being mentioned on here a good while back that disconnecting the battery for 24 hours did some kind of reset or reboot of NATS or diagnostic system. Hope you get problem sorted.