I'd suggest checking the new feathering shaft to be sure it is straight and then replace the O rings as well just to be sure. The blade rips always seem to have a little slop, and as you stated it's not much. You should also make sure the blade grips are secure.

FWIW, I cannot get my blades to track perfectly either at higgher rpm's. At 2350 rpm they are fine, but at 2650 they get out just a bit.