Strange "Hot Skin" Electrical Issue - Getting minor Shocks

I wouldn't think that the problem would be a grounding issue. You can ground out the power leakage so you won't get a shock alright but that doesn't fix the power leakage. Keep digging. Some of this stuff is hard to find even if you're an electrician. Testing from the trailer skin to the ground will only confirm what you already know. I would look for an outlet in your trailer that is wired backward or something plugged into an outlet that has the plug wired backward. Either one will somewhat electrify your trailer.