Problems with electrical converter

I have a 2015 Montana 3100RL fifth wheel. It’s began to blow the reverse battery protection fuses. I checked the battery connection and the white wire that is grounded to the frame is attached to the negative terminal on the battery. The black wire that goes to a terminal block is attached to the positive terminal of the battery. The battery is new and has a full charge. The 12 volt system seems to be working ok, lighting, carbon monoxide system, hydraulic jacks and etc.. Any suggestions what to check would be appreciated.