Alot of new RFI issues are being introduced all the time in the RV's. The lastest new source of RFI may be from recent installation of LED lights...
I know i had big time interference with my HDTV when using the OTA Antenna for digital signals from local towns, my WX ALERT RADIO, and My HAM RADIO setup all suffered from the LED installation. I never noticed the FM radio.
Another source of big time RFI is from almost any INVERTER setup. In my case the INVERTER would eat up my HAM RADIO operations especially in 7MHZ bands.
You can find out real quick if the LED lights or the INVERTER is causing interference by just turning them off and see if your FM RADIO jumps back to life...
Worth a check at any rate...
Roy Ken