I have worked on "new" RV's with the same problem. Somewhere the green "ground" wire is shorted to the white "common" wire inside of your RV. It usually happens when the manufacture wires in the converter. Have your repair person use an ohm meter to see if there is a short between the ground and common of the RV plug. (the plug must be unplugged, of course. Follow the connections from the other end of the cord until you find where the ground and commons are connected together. Separate them, and tie the whites to whites, and ground to grounds. A wire nut will usually do the job to connect the same color wires.
