I always use XP80.It's best for me. I am feel relieved that this problem is not occur only my XP80.I found it sometime.I generally found when sequencer is play.(also open direct from disk and from internal) I am shock when sound in any parts and any note become fuzz noise sound.It's loud. when I press to stop sequencer,anything is quiet .But when press keys, Sound is fuzz noise in any parts.It's deathly. I must turn powre off and on again. And other problems that I found. When I use more polyphonic (May be then 64) in sequencer,note will be delay (feel that tempo hear unstable) even if I will reserve each parts already.