So the ONLY thing that's changed is Cummins NorthWest put their meathooks into it. I still believe the fuel isn't adjusted right; can't put out enough propane to handle full load, but enough is there for partial load.
Try this;
It's a 2500 watt genny. Plug in stuff that adds up to 2500 watts. Start with a small space heater for example; maybe 1500 watts. Then a blow dryer at 1000 to 1500 watts. If your genny handles a full 2500 watts from those, then try turning them on at once, not one at a time. If your genny can handle that but not the AC and the Honda 2000 can handle the AC, then
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you might want to check the genny polarity of the outlet plug. They may have swapped hot and neutral or neutral and ground. Being as this is a built in genny, all three, hot, neutral, ground are probably all hooked up. A portable genny like the honda won't be hard tied to the ground, so it wouldn't realize a fault and not trip.
Hope something here helps.