MOTM

Can anyone help me out with this odd little quirk?  The PWM pot on one 
of my MOTM 300 VCOs is acting strangely - if you set the pulse width pot 
to its central position, it outputs a square wave as per spec, and 
rotating the PWM depth pot has no effect, but if you move the pulse pot 
to, say 3.00 position, then rotating the PWM depth pot changes the pulse 
width! (There's nothing plugged into the PWM in socket!)  the amount of 
effect the PWM depth pot has depends on the position of the pulse width 
pot - no effect whatsoever if it's centralised, and increasing effect as 
you turn the pulse width pot either left or right? Curious, eh?  I've 
checked for solder bridges & dry joints, but I didn't find any.  Does 
anyone have any suggestions?

Thanx!
-- 
Norman Fay