Majesty 7 piezo bleeding into magnetic amp – Help?

So my setup is my stereo cable to a homemade splitter box (basically the same as Dubaldo as far as wiring goes). Then the mono side goes to pedals and eventually the amp, the piezo goes straight to my acoustic amp. For some reason, the piezo signal is still audible when I switch to magnetic. I can turn the magnetic volume control all the way down and still hear a vague acoustic signal coming through. I did all the usual stuff like checking connections and changing the battery. My dad fixes electronics for a living but he can’t get it to act up on the scope so I was hoping some of you guys might have more insight into the circuitry. I also own a JP6 and using the exact same setup, it doesn’t have the problem, because I thought it might be a problem with the splitter or cable. I’ve spoke to Music Man and short of fixing it myself, I’d have to send it back to them for repair. As I can assume most of you can understand, shipping a guitar this expensive across the country makes me a little nervous, UPS and Fedex aren’t known for being overly careful with packages, not to mention the hefty shipping charges associated with it. And no, it’s not in warranty. Thanks for any help.