Did you by chance drain the water heater and later hook up to shore power before filling the w/h...that would burn out the electrical element and cause a ground fault ...there may be a switch on the outside of the water heater (mine did)...turn it off or disconnect the 110v connector and see if the problem goes away...if it does, go to lowes or home depot for a new element...much cheaper than rv supplier....I had the same symptoms on a previous 5er and that’s what I finally found after much searching and troubleshooting.