When you exercise the pots with the module patched into an audio chain (in this case, preferably patched directly to the output) and listen to the output, do any of the pots exhibit "jumpy" behavior or, with audio path controls, cause any noise in the module's output? I'm sort of entertaining a theory here that there might be some sort of contaminant in one of those pots, could be something like a stray speck of metal in just the right wrong place...