You might try looking at both ends of the pigtail. A lot of times, they have a quick connect where the bundle can be unplugged and replaced without splicing wires...it's possible that is working loose and getting shorted there. The other end may have something broken loose inside the actual 7 pin connector itself and may have wires touching there. I would try to unplug the pigtail if possible and then plug into shore power. If the lights don't come on, then the problem is probably with the pigtail.
2012 Chevy Tahoe LTZ - HD tow package
2017 Rockwood 2703WS Emerald Edition