Check the owners manual to see what items that circuit services.
Identify the plugs and other items for that circuit. Disconnect anything plugged into that circuit. If that means disconnecting bare wires then unplug shore power. Once everything is disconnected reset the circuit. If it stays on with shore power then an item on the circuit is shorted. Unplug the shore power. Check all the wiring at each item for short circuit. See if any wires looked scorched. Might be a bad receptacle.
Let us know what you find out what's on that circuit.
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