I have been playing with PID parameter. Now those seem to work quite well. Only YAW looses direction quite easily. I have been trying to set 2nd IMU, but it does not help with YAW. Next thing is to add potentiometer to YAW axis. But what happens with YAW when PITCH changes ad you seen in this vid ?
If "Use frame IMU, if possible" is checked this occurs, but unchecked deviation does not seem to happen. Also frame IMU is calibrated (more than once). I had previously 8bit contoller, but upgraded to 32bit because of stability issues.
You should firs set it working with Camera IMU only and then add frame IMU. It will work ok at least+-30 degrees deviation from level without frame IMU.