Ty, I just purchased a 5th whl in June, and this never happened to me, until a couple of weekends ago. FRUSTRATING is an understatement. One of the assistants at the RV resort suggested I use a 50/30 reducer. It kind of looks like an extension cord, and mine ran $25. After about 4 hours of the breaker tripping every five minutes with just the AC running, the 50/30 reducer did the trick.
My RV dealer had lots of them, so I do suspect this isn't all that uncommon.
The more current that comes through your electric cord to the park plug/breaker the more voltage is produced from one end of the cord to the other. If this voltage is produced across the cord, then that much voltage is not available for the RV to use. Saying it another way, the RV has less voltage available if it uses more current.
At the same time, the motors in your A/C draw more current through the cord as the voltage gets lower.
So, you see that two things go on at the same time to work against you.
And to top it all off, the park's supply voltage probably starts out low because there are so many RVs in there doing the same thing as yours --- cooling and cooking! (This is probably a summer time condition, too.)
The trick that Amy got into with the 50 amp receptacle is that there is probably a separate circuit for the 50 amp plugs and/or there were/are fewer users on the 50 amp supply. Meaning that the voltage was higher.
Also, the connections (plug/receptacle) are part of the circuit, too. If these are not really tight, then there will be voltage loss there just as in the cord. I keep my plug contacts bright and shiny, too.
One solution is to use a voltage boosting transformer that detects the low voltage condition and boosts the voltage to your RV. I have one, and I haven't had any problems with blowing breakers.
Your dealer is wrong. All 30 amp systems don't blow the breaker in those situations. Mine doesn't.