@Roby > If you want to change the defaults of the SX mapping, there's a bit of monkeying around to do, but I'm in the midst of creating a guide to doing this so I'm not going to post how here.
If your AKAI sends the same MIDI signal on the same channel as another signal from the SX, it will encounter that error. You may be able to change the output MIDI channel on the AKAI so it doesn't conflict.