I have a Ketron XD9-Great machine-good sounds,but I have this problem and i'm wondering has anybody had the same happen and is there a solution.Talking to some people that I think should know,they don't seem to know what i'm talking about,but these are engineers ,not musicians.I need to play a lot manually,ie.arranger off and no drumbeats.Right hand is fine but on the left with the keyboard set to BASS+LOWER I have a bass which is ok but having put instruments into the two lowers available in arranger view if I attempt to alter the volumes of these they are likely to mute and not sound at all.I am then left with a bass and right hand .This is not acceptable and the machine did not always behave in this way.I can right it by turning the keyboard OFF and then on again.Can anybody help.Can I do anything myself.It does not happen all the time and the engineers say they cannot do anything until it happens and stays there.