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Check the breaker on the set and if that is good, the next place to check is the automatic transfer switch to see if that is acting up or bad. That is a black or silver box at the terminus of the shore cord and about 9" or so square. The cover comes off for some testing. You will need a small digital multimeter for that. About $20 or so at most hardware stores. I can direct you in the testing. All follow ups are included in our fee.
Just checking back in to see if you got this resolved or do you still need some help and additional input from me here?