Not quite Bulletproof

Today, I hosted a MEETUP group - the South Bay Quadcopters.  It was a good time, even though that only 8 of over 85 "members" showed up.  

I got to try some FAT SHARK goggles for the first time.  I was flying my little 6" "pocket rocket" (250 mm quad).  I had a 5.8GHz 600mW transmitter and a Sony HD camera sending the video to the ground. While wearing the goggles gave me a whole new perspective, it was disconcerting because while I could (only) what the aircraft could see, I didn't know where it was in relation to me.

I think that with a little practice, I could quickly overcome my disorientation.  So I'm going to buy some!

I did a test flight of one of my bigger quads (12" props, 6 lbs, full gimbal, FPV, GPS, etc.).  I noticed that when I first armed it, the right rear prop didn't spin.  So I disarmed it and armed it again.  It started this time.  I should have known that something wasn't right and tied it to something heavy and cranked up the motors - but I was at the meetup, so I sent it into the air.  All was fine for a little while.  Then the quad came plummeting to the ground.  At about the same time it hit the ESC controlling the right rear motor was ON FIRE! I ran over and blew out the flames.  I wanted to make certain that nothing else burned. Fortunately, I got there before several hundred dollars of "stuff" burned.

So what happened?  I am convinced that the ESC was defective and led to the mess. The ESC was an expensive, (supposedly) high quality one.  Of course, it was made in China - but they all are.  I have attached a picture of the burned ESC, and another picture of a new one.  Note how the label calls it "Bulletproof". I somehow question that designation.