Trad Heli Crash

#1

Hi,
I had a crash few months back with my Trad Heli which is a 800 size gasser.
Heli was in “Loiter” mode about 5 AGL moving forward, very slowly, with my forward command stick.
suddenly it banked hard left and nose down and crashed.
I have been unable to figure out the crash reason. I am quite sure it was not a mechanical failure and not power related. Heli has a generator and the battery voltage was good.
I have replaced the carrier board just incase and updated the MP and the FW to the latest. Had a flight yesterday and received the Critical SB message from MP.
Would appreciate any help so to figure out the crash cause.

Link to crash bin: https://drive.google.com/open?id=1FryxFK-r2mZPjdc6XvT5oigxAqpa4jc1

Link to Critical SB message flight: https://drive.google.com/open?id=1fr6OoL0D9NWv8V1pqi4mzrA5xMzlLJOU