Not sure if this will help, but its still good to know:
1-the hardware MUST have a solid earth ground for the faders to function correctly, so check your power cabling(you can't cut the ground pin of the AC plug or use one of those little adapter blocks from Home Depot).
2-the fader caps are conductive to sense capacitance in your skin. Swapping fader caps for plastic caps is a "no no".
3-if the climate is extremely dry(like it can get in winter), that can interfere(not sure if a little hand cream will help as I've never seen it bad enough to need).
4-back to the grounding issue, you can try connecting a piece of wire from the AC ground(the center screw of an outlet cover) to the chassis of the PC. You could also try wearing one of those grounding straps for working on computers.
Based on your exact description, I mostly suspect that the main unit has a grounding issue. Hope you work it out
