So, it boils down to OPERATOR ERROR in the end. He reversed the throttle servo and didn't rebind it.

Why it went into failsafe is anybodies guess.

I like Spektrum and trust it. I made a mistake in setting up my first model with Spektrum and almost lost a $3500 plane. I saved it and figured out why it was not working right. My fault for not setting it up correctly. It's fixed now and rock solid.

Basically:
If you make ANY changes to a Spektrum setup, you need to bind it again.. If you adjust an endpoint, bind it. If you reverse a servo, bind it. If you adjust any sub-trims, bind it.

You bind the system to do your initial setup on the bench. That just gets the TX and RX talking to each other. Then you bind it all again when you're finished dialing it in.

If you make ANY changes to the endpoints, channel reversing, subtrims, etc etc etc...... BIND IT again!!

Go fly it......maiden flight. Use TX trims to establish hands free flight..... flat and level.

LAND IT!!

BIND IT!!

If you so much as SNEEZE at a Spektrum radio, BIND IT again!!

Overkill? NOPE. Pain in the butt? Yup.... Necessary? I believe so.