50 ~ volts in door/doorframe, intermittently

Thanks for the suggestion, but unfortunately for me, I'm afraid it's not going to be that simple. It's happened with and without the adapter. The ground coming in to the unit from the power source, and power cable has been confirmed as good to go. It's happened at 3 seperate power connections, both with and without the adapter. Each tech and the licensed electrician that has had a go at it all agree that there is a Neutral/ground issue. They seem to believe that the neutral is touching something it shouldn't be touching, causing the volts to travel through the frame (the RV door & door frame). Any other suggestions or does anyone out there know how to possibly troubleshoot or isolate the problem without it actually occurring? as in, when there isn't voltage passing through the door frame but all systems are on and in use?