You had two 1500 watt heaters (roughly 12 amps each) plugged into one 15 or 20 amp breaker, Yes, it tripped, that is what they call Working as designed.
Next time make sure when you plug in a portable heater it is on an outlet that is *NOT* powered via the inverter.
In fact, a suggestion... 12 amps is pushing it for many RV systems.. Though the outlets are rated for 15... 12 is pushing it.
I installed a pair of 15/20 amp breakers in my RV, one in the bedroom, one living room. These outlets have a T shaped neutral slot and will accept either 15 or 20 amp plugs. (20 amp plugs the neutral is turned sideways)
They DO NOT have any kind of hole or punch down connector but rather a screw you bend wire around and tighten down.. 12 ga wire is what I used, and it runs back to the breaker box where it has a breaker all to it self..
I also have a 3rd 20 amp outlet but it's kind of special and I won't discuss it.
These are for the heaters... No problems, no smell of hot wire either.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times