Pixhawk cube and here gps quadcopter land inbetween mission

I am attaching the log file here, my mission was actualy 5km one side has done before with same quad 2 days before, now for the second time the quad land after few km, without any crash.
there was no telimetry or radio range while the landing happend, please help what is wrong with it
i swear it looks like an ekf/dcm faiksafe as the magnetic field is higer than 95% where while testing the mag field was way below 4%
what will be the problem?
attaching the log of the described flight

https://drive.google.com/file/d/0B-73ECyqOvYAMm1vYUMyZXktYlk/view?usp=sharing

Your log shows a switch in flight mode from Auto to Loiter, back to Auto, and back to Loiter at which point you have the throttle at minimum and the copter did exactly what you were telling it to.

But I didn’t had radio signals at that point. And I didn’t moved any switch…
Is there anyway it will happen automatically? Or any other reason?

You are a life saver Mike… hope this will fix my prob… actually the failsafe was not triggering and whenever my radio signals goes out its is moving the own to loiter and throttle to lowest hence it’s acting like this…
Let me try another mission and update you