Unexplained Copter Crash

Hi guys,

I had an issue with my Drone a few days ago, DJI S800 Evo, PIXhawk 2
Basically I selected auto for a mission… on the laptop,
The drone took off to 20m, then just sat there… didn’t head to WP1, just sat there…
So selected loiter on my controller and landed and disarmed, then as I reached for my laptop the droned armed took off to about 10m yawing at a bit of speed, strange, then motors cut out, and drone dropped to the ground .

Not sure what went wrong…
Could you please help diagnose

2016-11-03 12-10-03.bin (1.3 MB)