Last month while setting up at an older RV park the power pedestal initially showed 120V on both 50A legs, both via multimeter & surge guard (TRC). Five minutes after starting one air conditioner though, the TRC tripped off indicating 141V on L1, 91V on L2, and reversed polarity.
I unplugged, cycled the pedestal breaker, and plugged the TRC back in (with shore cord disconnected), but it still showed the same bizarre high-leg/low-leg/bad polarity power conditions.
Between this and a busted water spigot, I got the park to move me to a different site and had no further problems that weekend. Still, the TRC saved me from some likely unpleasant consequences due to bad power at the podium.
That's also the first time I've ever seen both high and
low voltage concurrently on the same receptacle.
Hopefully the park's new owners (who had just taken over the park the week before my stay) have since repaired that issue...