If I understand, you're using a 30->15 adapter at the post; a 15A cord in the middle, then a 15->30 adapter at the trailer... You're overloading the 15A cord you're using the the middle. It's actually a pretty dangerous setup you have there.
Guessing the A/C compressor wasn't getting enough voltage to start, and was locking up... That's bad for the motor.
Without getting way into it - the smaller the wire, the more resistance; the more resistance, the greater the voltage drop. You also heat up the wire, which creates a risk of damage, or even fire...
Getting a 30A extension is the proper solution - or if you're going to use a 15A cord, don't use the 30-15 adapter, and plug into the 15A outlet at the post. At least then the breaker is properly sized, and will protect the cord. And if you are using a 15A cord, with or without the adapter, don't use the A/C - you're overloading the cord.
2014 Grey Wolf 28BH, behind a 2015 F350 Diesel Crew Cab
Nights Camped 2015: 37
Nights Booked 2016: 44
Nights Camped 2016: 41