Problem with maintaining Yaw during missions

Hi
I have a problem with my copter in AUTO mode.
Every time the copter flies throughout the waypoints , it cannot keep it’s heading even though I have set WP_YAW_BEHAVIOR parameter to “Face next waypoint”.Here I am going to attach data flash log of my mission.The copter flies throughout a straight line and then eventually lands.

Many thanks,
Babak
00000142.BIN (920.0 KB)