Diagnosing Dataflash log

Can you help us understand another crash? This one involves the Pixhawk 2 we bought from JapanDrones. We attached this to a quadcopter with a DJI F450 frame. We want to test this using waypoints in Auto mode. It took off smoothly and it reached the first waypoint as expected. However, after the first waypoint, it immediately returned to launch due to radio failsafe and before reaching the home location, it crashed. We also tried to understand the dataflash log but we cannot figure the main issue. Thank you.

2017-12-13 12-36-02.bin (476 KB)