After talking with Fran, I ruled out a motherboard issue. The sounds and features all work, EXCEPT those few keys I mentioned. This is most likely a short, or crack in the circuit board. MIDI works as it should, as do the recorder, players, rhythms and sounds. "SOMETHING" in the keybed, or connections has failed.

I retired the unit to sit atop my Rhodes and serve as a sound source, a monitor amp/speakers, a quick MP3 recorder, and general cool stack topper.

How's it look?
(The kb stuffed in the middle is a Korg i5s that I got from Boo. It serves as a controller for the 900, so I don't have to reach) I play bass lines, and accent sounds on that, while I comp on the Rhodes. Like the old days