Check the voltage from line to line. It's possible that the 78V side is being backfed thru electric water heaters and electric dryers (240V loads) from the side with the 120Vs. You'd see 120V-78V=42V, which would vary depending on how many light bulbs and such are turned on on the 78V side. But they should be complaining about a lack of hot water. And that the 78V side has a disconnected 120V up from the meter socket to on the power pole transformer or elsewhere in the POCO territory. Are the houses in the same neighborhood, fed by the same transformer?
