The problem started with the first failure, which was most likely a loose connection. No matter how hard you tried to clean up the connection, once a terminal is overheated, no matter how tight you make the connection, it will fail in the future. The contractor needs to be replaced. Since the failure was due to a loose connection, I would be surprised if Progressive repairs it under warranty, but it is worth a try.
Since most overheating is caused by loose connections, and a RV gets lots of vibration compared to a house, it is worth taking the time at least once a year to power down the RV & checking & retightening all the electrical connections including both 120V & 12V in your converter.