Those were good things to try.

I just checked something.

Speaker Calibration interestingly Selects RADIO on the Speakers.
At least on a G61RSL it does.

MRC Selects CD.

So MRC and Speaker Calibration are different.
If the Speakers are correctly typed it doesn't matter if it's RADIO or CD.

If a Speaker is TYPE 5, RADIO is on D2 and CD is on D1.
If a Speaker is TYPE 6, RADIO is on D1 and CD is on D1.

Like I said earlier try moving from D1 to D2 (just as a test for MRC).

Also as I suggested try skipping the front speakers and see if the rears work.

If it is hardware, which I still doubt, try swapping Left and Right Speaker and Retype them accordingly.

A bad cable might cause some weirdness too.

- Fiddler (IMHO)

If you think listening to music is fun, try learning an instrument.
HT: G61RSL, 4x5K, 5.5KHC, 2xSC6000, Transporter, HD621, Philips BDP7501 4K, Tivo, 65" LG OLED 4K C6
Computer: Foobar2000, 5K, Mojo, HiFiMan HE1000 V2