Unless I missed it. I didn't see anyone suggest switching wires on breakers to see if the problem moves. Another suggestion is to take all the dead receptacles loose and pull them out to inspect the wires. It is possible that you have 2 problems. They are really tough to find. I was an industrial electrician for 35 years. If you rv has been ok for ten years, I see no reason to think any wires have been switched.Keep us posted on what you find. I tend to agree that a digital volt meter will not load the circuit.Another suggestion is to make sure that you push the breaker to the off position before you throw it to the on position.