Pixhawk 4: Manual mode- initial negative pitch before take off

Hello !
I am using pixhawk 4 on DJI F450. Whenever I get the throttle stick to 50 %, my quad pitches in negative direction. Please note quad is completely balanced, no CG offset. Additionally, sensors are properly calibrated. This happens only intially. Once I take off I have control on the drone. Please find the log link below,
Any help is appreciated ! Thank you !