Pixhawk with Arducotper 3.2.1 firmware crashed

Hi Guys,
Today i was testing my pixhawk on a quad copter with 3.2.1 firmware. I had sent it in autonomous mission. It crashed while returning from the mission around 2.5 km away. I saw the data flash logs but couldn’t conclude anything. So please help me out in finding out the possible cause for the crash. I have uploaded the log file also with this post.
I had similar crashes with APM on board with the same firmware some time back. Please help me in finding out the cause for the Crash.

i have posted same issue in DIY Drones also

here is the link with the log file attached in that post