The player may have a fault (albeit rare on the Rio-branded units) where it always thinks it is on car power

Wow I never heard of that one! I thought it was the opposite, where it thought it was on home power in the car due to the leaf switch making contact when it shouldn't (or something like that.) I had this problem on my Empeg and had to send it in, and had it happen to my RioCar until I messed around and tweaked the leaf switch. Since then I haven't seen it.

Didn't know the reverse (thinking it's on car power all the time) was possible.