Disklavier

I have a fairly new DC2B (Mark III, with record, DKC-60RCD controller).  Serial number 6215XXX.

When playing songs thru it, whether from built-in songs, to PianoSoft discs, to downloaded MIDI, the piano drops half of the notes when the volume is at the softest level (-10).  

It seems like a huge jump in volume when you go from the softest (-10 LED is lit) to the next higher volume level, (-10 and -8 LEDs are lit).

I don't have a calibration manual or know anything about performing a maintenance but I can learn that if you think this issue is related to calibration/maintenance.

Thanks in advance!

Joe