VPI JMW grounding issue

Not sure where to post this, so I'll try here. my VPI JMW Memorial tonearm has developed a noticeable hum. The hum increases when I touch any part of the tonearm, so I'm assuming it's a grounding issue. I've swapped cables, (except the leads from the cartridge), phono preamps, and cartridges, with no improvement. Is there an easy fix that I need to know about? Is there a service that will rewire/upgrade the internal wiring? TIA for any assistance.