30 to 50 amp. Problem adapter/converter melting and failing

Sounds like you are trying to pull too much current for the 30A wiring and overheating the connections. Better fail there than inside you house or coach. I run a 50A coach on a 30A outlet and cord all the time, and have no problems. Bet I don't try to run two ACs a heater, and a coffee maker and hairdryer all at the same time. And yes, I have burned up a few connections over the years. The rule is if you burn a connector, you are overloading somewhere.