Need help to analyse tracker poor performance (with DF log)

My antenna tracker V1.1 is running on Pixhawk. It does not track the vehicle closely in terms of both yawing and pitching. Tracker yaws and pitches, but far from aiming at the vehilce at any time. It also behaves the same when testing with SITL. I attached both the DF log and the param for analyse.

For the convenience of whoever can help, I graphed the Des Yaw vs Yaw, Des Pitch vs Pitch, and the RC out (C1 and C2) to both yaw and pitch servo in repsonse to the vehicle (a quad) movement.

Altitude source set at 0 (= barometer). Both servos are set at Continuous Rotation.

What param should I adjust, and in which direction (increase or decrease) , PITCH2SRV_P and YAW2SRV_P, or other param to make it track closely ?

Appreciate your help.