The first thing you need is a voltmeter to see what the CG voltage is like.
Low voltage is common in CGs and you won't always know in advance what it will be like. It's usually worse in the summer with other RVs all running AC units at the same time, and then can worsen further at dinner time. Older CGs are typically worse than newer ones (built after 2005). Casinos with RV sites, more "upscale" RV parks and some gov't CGs can have rock solid 120 volts as they went above min. code requirements. It's always a very good idea to have a voltmeter permanently mounted inside.
When the voltage goes down, an AC unit draws more current. An AC unit will momentarily draw around 5-6 times the full load current (at it's full nominal nameplate volt rating). The 20 amp breakers are sized based on the full load current at the nominal voltage rating, which is approx. 15 amps. So an AC unit will draw approx. 90 amps at startup, and if the voltage is low at startup, the inrush current will be even higher which will trip a 20 amp breaker.
Depending on how low the CG voltage is (at the pedestal) and what other loads you have running when the AC is turned on, sometimes the 30 amp breaker in a pedestal will trip. It could be the 30 amp breaker in the converter/panel that trips, but is usually the one in the pedestal.
If the voltage gets too low, as in below 105 volts, damage to the AC unit will occur and is cumulative over time and if you keep running the AC unit with low volts, it will eventually fail prematurely. You really need to ensure the voltage is healthy at CGs and having a permanently installed voltmeter will help a lot. Having an EMS unit (Progressive Industries for ex.) will automatically shut down on low volts.
You could try shutting off ALL other loads by turning off breakers in the converter/panel and leaving on only the AC unit as this will minimize voltage drop inside your TT. If it starts okay, then it would be a voltage drop issue.
Sometimes voltage can be low enough that you won't be able to run an AC unit and there's nothing you can do except for using an autoformer to boost the voltage.
If you take the TT to the dealer, they probably have decent voltage at their shop and they won't be able to replicate what is happening at a CG that has low voltage. If you do use a voltmeter at a CG and know for sure that the voltage is good and the breaker still trips, then it would be worth taking it back to the dealer.
