Help requested to analyse Qplane crash at first forward flight

I have modified my Bixler2 to quadplane and test flown in QSTABILIZE mode twice without problem. Today, shortly after taking off in QSTABILIZE, I changed to FBWA and after a couple of turns at low altitude, the plane suddenly yaw uncontrollably and crashed. Pls see attached log and param and suggest the possible reason of crash.

Thank you,