I put the converter back in the camper and tested it with lamp only. The output load dropped down to 12.24V DC and label on the housing shows output should be 12.3V DC so the converter seem to be working fine and working within the normal parameter that it was designed for.
I think I know why converter breaker was tripping now. Seem to be a possible short between the refer and the converter but surprising it never blew the fuse.
Also it look like previous owner added another ground wire to the neutral (white) terminal bar to the trailer chassis. There already a ground from the chassis to the ground bar so I believe that was tripping the breaker at the camp site with the new ground fault protection. The extra wire doesn't look like it was installed by the factory.
All the lamps are working which were one of my primary goal to have working without spending any or whole lot money on.
Bill