VTOL - Extreme Pitch Servo2 Output when transition

Hi All, Please help…

What is causing extreme pitch (Servo2 Output very high) on VTOL transition on any flight modes (Stabilize, FBWA, Auto) as shown on the graph below:

Every time the transition started, RC2_Out (Elevator) will output very high value causing the plane to flip upward, even though there is no movement on the TX - pitch stick and the ATT.DesPitch was 0 degree but the Servo2 Output (RCOU.C2) was very high. I tried the transition using Stabilize, FBWA and Auto Mode with same pitch problem.

CoG was spot on balanced and Servo movement going to the right directions on manual and stabilize mode.

Detail Plane:
Firmware: 4.0.9
AUW: 5.2 Kg

Please see the problem on this video:

Link to the Log File:

This is my third VTOL setup with the same hardware and parameters, others are flying very well.
Please help me to analyze what is the cause of pitch problem.
Many thanks in advance