Issue with Pixhawk 6C AHRS_ORIENTATION

I am using Pixhawk 6C with ArduPlane v4.3.5. The FC is mounted in the non-default position - YAW 90 on the frame but the GPS is mounted in default orientation. To set it up, when I set the AHRS_ORIENTATION parameter to 2 (YAW 90), and calibrate the compass, the calibration is completed. However, the heading shown is incorrect by 90 degrees. If I disable the internal compass and use the external compass only, then the heading shown is correct.

When I mount the Pixhawk in default orientation and set the AHRS parameter to 0 and then calibrate it, then the heading shown is correct.

I have used Pixhawk 4 instead of Pixhawk 6C and have not faced any issue. Please help.

@tridge Can you please help? Sorry to bother you