Did you get a message that indicates a problem or some form of odd characteristic in flight?
Props balanced ? You could try bit of tape on opposite side of yaw drift which will rule out unbalanced props or prop,,are all motors spinning same speed,,compass been done to eliminate it too,No message, but I still have yaw drift that make still photography difficult. I calibrated the controller sticks, but wanted to learn more. What a shame that these aircraft controllers do not have trim pots to fine tune the crafts ability to hover still. The drift is very unpleasant.