Shorts blow fuses, Loose connections do what you observe.
On my motor home the Pioneer radio did exactly that.. Turned out to be working fine.
However on my RV the "House" radio is a 120 volt home theater device, also Pioneer, very nice, many advanced features.. no need to list
But the SPEAKERS... are shared
A relay box (Which on my Workhorse chassis W Series is behind the parkign brake pedal,, but in truth could be mounted most anywhere) selects HOUSE or DASH radio based upon the status of the ignition key accessory circuit.
Well, there is a line of RCA cables (like the red/white/yellow video/audio cables) all were firmly connected.. What I failed to notice was a pair or 3 MOLES plugs right above them (Multi pin milky white plastic things) These are latching plugs.
Pressed one, Heard the latches go SNAP (lock into place) and now the only problem is I have to pay the barber to cut my hair once again.