I have an opinion on what we are observing. Wayne, I think in your 0.4 VAC case we are measuring the VAC drop on the Neutral Wire as I have shown in the Top Circuit.
The 0.4 and 2.2 VAC Joe and I are measuring is the voltage drop in the bottom circuit and is developed by the small current (~ 1.5 AC mA) flowing through the Earth path. The Earth Resistance on my 0.4 VAC is in the magnitude of 165 OHMS. In Joes case (2.2 VAC) there is either a bit more current and/or higher resistance. It might mean that Joes RV is located further away from his Ground Rod then my RV is from my Ground Rod.
Then there is also possible soil conductivity differences.
