In an attempt to understand the absolute full extent of the battery payload, a field operator had conducted a test allowing the copter to loiter until it "fell" from the sky. I know, I cringed hearing this also. The following days flight resulted in a failed takeoff the first try (flipped on the launch pad), then an erratic flight to about 10 meters when the throttle was cut and an abrupt landing followed. There was negligible damage  to the aircraft. I felt like the symptoms described un-calibrated or damaged ESC resulting from the low voltage cutoff.

I am downloading the dataflash files now  I have an idea what to look for. Roll demanded bu the autopilot relative to actual roll and same with pitch. Anything else you would look for. 

Thanks