Neil,
I’m sorry about this trouble.
I’m not sure what is happening here. Does the frying sound happen when the treadle is stationary, or just when it is moving through the lowest part of its action? There are some interesting things that are happening at the very lowest volume setting that may be causing some sonic artifacts. I’ve never heard of this happening, but I suppose it’s possible.
A question that follows is how much gain are you using on the VPM-1 or after it? If you use a lot of gain, then some of the normally inaudible artifacts might be more audible if the volume is turned up enough.
Also, it may help to re-set the volume level table in your pedal’s software by running the “stereo setup routine” discussed in step E-3 of the troubleshooting guide (if you haven’t done this already).
I hope this is helpful.
-Brach