Battery Switch questions or is it a ground issue

Hmmm....I'm going to have to think about this one and follow along. Like @MDchanic , I want to help as I find these electrical issues fun to troubleshoot (yep, I'm an engineer!). But the internet makes things lots harder to communicate so we're a bit balled up trying to understand what you have.

My understanding is with the switch in the On position, life is good and you have no 12v power to anything like the roll cage or chassis bolts. But when you turn the switch to Off, which opens up the negative side of the battery to chassis ground, now you are getting 12v applied somehow to your chassis. Sounds like some type of weird backfeed...but where? Let's see what some of these other fellas (or gals!) might have to offer for ideas. Collectively, someone on here will nail it!