Any one else had this.

[Trebus]

Have you ever had them out? In my experience the manufacturers never use enough grease and often they are dry. Not necessarily to cause a knock, more stiffness. You can grease them without dismantling the front end completely, obviously the stem nut and adjusters need to come off along with the yokes undone but drop them down an inch and gob a good dollop of grease in. Then adjust up and try. To check them beforehand you need a jack or a helper to push down on the rear with it on the centre stand. Give them a good wobble back and forward and check for play.