WFCO Converter tripping house GFCI?

[FairviewFairyFarm]

Hello everyone! My TM has been tripping the 15amp GFCI in my garage and I have traced it to the converter breaker on the 120v side of the WFCO 8955 panel. When I plug into nongfci outlet, the DC reads at 13.4v, which makes me think the converter/charger must be working somewhat correctly? What could be causing that GFCI outlet to trip, but everything seems to function normally when plugged into standard outlet? We are embarking on a trip soon and don't want any issues on the road! Thanks for all the info, this forum rocks!