So are you saying it is still drifting after that? Then are your blades tracking in the same plane? And are your flybar paddles parallel to the flybar cage? Do the links move freely and not stick on anything? After all that and it still drifts just add some right aileron trim and that should get rid of the drifting.

When the motors are unpluged and you move the throttle up does the swashplate tilt to the left?

Nick