Yamaha DTXpress/DTXplorer/DTXtreme

Just got my module back from the tech Yamaha had my local music store 
send it to.  He claims not to be able to re-create the problem I'm 
having, and I wondered if anyone here has a similar issue with the 
DTX III.

I have two keyboards & the DTX (Special) pads as controllers, and a 
number of sound modules hooked up to a mixer.  Two problems:

1. The only sound module I need to add gain to is the DTX III.  For 
some reason, it has the weakest signal of all my modules.

2. This is the wierd one, which I probably wouldn't even hear if not 
for #1.  If I play either of the keyboards, which send MIDI note 
messages to the DTX, I can hear clicking coming out of the DTX's 
audio channel even if the DTX is turned off.  I've isolated this to 
the DTX itself.  If I connect a keyboard's MIDI out to the DTX's MIDI 
in, turn off the DTX, and play the keyboard with Local Off and all 
other mixer channels muted, I can hear faint clicks coming out of the 
DTX's audio outputs in response to the Note On messages coming into 
its MIDI in.  Unplug the MIDI in from the DTX, or the audio outs, and 
the problem goes away.

Anyone else have these issues with the DTX III?  Any advice now that 
the repair guy can't hear this?

Thanks.