I have encountered pedestals with serious defects {detected by my Progressive EMS} more than a dozen times. Anyone of those defects, bad, ground, polarity, neutral etc. could have spelled disaster. I have had our EMS shut down low voltage a number of times any one of which could have cooked by AC compressor or done other expensive damage.
For what you potentially have to lose spending around $300 {for a 30 amp EMS} is small change that buys a great deal of peace of mind. Do you have insurance on your RV? Think of a quality {Progressive} EMS as just an additional level of protection as your RV insurance will not cover the damage that the EMS will prevent.
As always... opinions and YMMV.
:C