By specifically excluding lightning as the high voltage source, the surge protector really does not have an explainable source of failure. Did other users on the same distribution circuit have similar experiences. An excavator cutting an in ground line could possibly give a momentary phase to phase voltage level but the distribution circuit protection should be fast enough to shut it down. You really want to have a qualified electrician look at the set up for both the fifth wheel and the power source to the fifth wheel. Instead of an rv 50 amp supply you may have an electric dryer 50 amp supply. Difference is 120 versus 240 volts.
pops
