50 ~ volts in door/doorframe, intermittently

Harvard, if I understand correctly, you are suggesting that there may be an opening in the ground somewhere between where the shore power cord comes into the RV junction box and the breaker panel? Thats a tough wire to trace in my RV, I suppose I could put an ohm meter and test continuity between the junction box and the fuse panel, is that what you suggest? I think that if the system is functioning properly, i.e. I have my receptacle tester plugged in, and my multi meter hooked up to the doorframe, and I'm getting no readings, then all will test out fine…..but I know that it's not all good, because I've witnessed 50v on the multimeter and an "open ground" indication on my polarity/receptacle tester on Friday, and last week 2 other folks experienced a shock or tingling at the door frame.