Originally Posted by The Fixer
Both cups and fork crown race pressed and seated as far as they go?
That would be my question too. when you installed the cups and race did you use a proper press, or did you just whack them in with a mallet? To me it sounds like the cups or race are seating further as you ride thus introducing play. make sure they are fully seated before you adjust your headset otherwise it will keep loosening until they are.