2012 Kodiak 200QB Electrical Issue

[senoiasummer]

Hello all,

I am the second owner (at least) of the above model travel trailer. My Brother in Law owned it before me and as far as I can tell the trailer was well maintained.
I have owned the trailer for about a year and its been out three times (twice by me, once by my son), all short trips.

Both my son and I have Ford F-series trucks, mine a 2018 F-150 and his is a 2019 Super Duty. We have both seen a random "trailer wiring fault" flash up on the instrument cluster. In the most recent trip, I pulled the trailer from home to CG, about 250 miles and never saw the fault. On the way back, I saw it once early on the trip back. I didn't stop the truck and check, but I know the running lights were still working on the trailer.

Additional, on this trip, for the first time, I had something odd happen with the GFCI in the trailer. I was connected to CG 50A service. We arrived at the CG around 1PM and all things electrical appeared to be working. We have a nite lite plugged into the GFCI (which is physically located in the bathroom) which was on, so know it was working. That evening when I plugged my iphone charger into one of the outlets up front and it wasn't charging the phone. I checked another outlet and it wasn't charging either. I went back to the bathroom and the GFCI was faulted. I reset and the charger worked and I went to bed. At some point during the night the GFCI tripped again. I reset it and didn't have any additional issues for the remaining two days of the trip, which included having iphone and iwatch chargers plugged in, coffee pot plugged in and brewing, and waffle iron plugged in and working.

What are the chances that the two issues above are related? I haven't look for or at a wiring diagram yet, as we just got back last night, and I am at work today. Is the 12V ground wiring from the truck isolated from the 120VAC wiring? I assume it is, which makes me think that I have two independent problems.

Thoughts? My inclination is to start by looking at the ground wiring in both cases. I took a brief look under the trailer when we got home and I see a single jacketed, presumably multi conductor, cable running from the hitch over the axel and back towards the back of the trailer. My first assumption is that if the outter jacket of this cable looks "ok" that the interior conductors are "likely" ok as well.

Thanks for any insight!!

SS