Dirt could definitely be doing it. But if that's the case, the surge protector sounds like it's doing its job. If you didn't have one, you could be seeing current surges way too high for some of your on-board appliances to handle. Or, the dirt/mud could be affecting your correct connection to ground or neutral. Either way, the surge protector is a good insurance policy. Sounding like they need to get an electrician over there to clean up that receptacle. In the meantime, if you can move to another site and another power pole, you're likely better off.
2006 Jayco Seneca 34SS
2006 Jeep Wrangler Unlimited Rubicon Toad