enblethen wrote:
There seems to be an open in the ground in the pedestal wiring. When you energize the GFCI receptacle, a ground path is made possibly through the neutral of the 120 volt 15/20 amp circuit.
Energizing the GFCI should not create a ground path via the neutral. The GFCI mechanism itself does not even need or use a direct ground. The only reason one is connected to a GFCI at all is to provide a safety ground for 3-wire devices plugged into the load side. The neutral should not be bonded to ground on the RV end per the NEC.