It sounds like low voltage and could be a CG issue or your cord plug. If you could have measured the voltage at the pedestal or inside (both legs) that might offer a clue. Can't really tell where the power got interrupted.
Your surge/transient protector is just that - SURGE/TRANSIENT DETECTION ONLY. It is NOT a power protector, it does not shut down power. This is in contrast to the more common RV Energy Management System (EMS) which detects high/low voltage, miswired pedestal, open neutral and other faults and disconnects the power. Your unit is very expensive and may be quite good for surge/transient (pure surge if you like).
I also recommend the PI HW50C. My remote is inside and I can observe voltage/amps and faults. HIGHLY recommed this unit as it also protects against an open neutral which if that occurs on 50A will let the smoke out of your electronics. I bought mine in 2004 and it's now in the second RV so I like to say it's free.
I've never had a surge that caused the HW50C to fail but have encountered all of the other faults. Low voltage is rather common on 30A pedestals and less common in my experience on 50A, only happened to me once - hot summer day, older full park with many AC's running and I had 3 cranking.
FYI Parks like homes are NOT wired to provide full power to every pedestal at the same time. Instead they are wired assuming full power will not be needed to every pedestal at the same time due to appliance usage/cycling. Normally the total power available is about 40-50% of the CB ratings.