When did the problem start?
On a trip or just since you plugged it in at home.
Have you attached anything new to the camper. I had a buddy once attached a bracket to the outside of his trailer. The screws he used tapped into one of lines going to a wall socket. You would wet your shorts when you grabbed the door handle. :B
The converter is only tied to one AC breaker and turning off that breaker would kill the problem if it was a shorted converter. The problem is progressive (spread across multiple breakers.)
Bad ground and/or common connections.
Unplug the 120v AC, loosen and retighten all connections to make sure they are tight. I say loosen then tighten since if there is some corrosion at the contacts it will clear this issue.