Drone yaws in sudden when switch from offboard to auto.land mode

My program triggers auto.land in offboard mode. The drone is able to descend nicely until when it is very close to the ground, it yaws in a sudden. By looking at the log, I found that at the moment when the drone switching from offboard mode to land mode, the yaw setpoint changes immediately; and I also found that the yaw setpoint is been set to the east. Does anybody knows why the yaw setpoint changes when switching to land mode?

The log is here: https://review.px4.io/plot_app?log=9e75b2cb-e918-4565-9068-c6bca37e84e9