Yeah , most of the Hagons etc have a little bit of head stem movement, I have a grease nipple in my Hagon's head stem as well as the fork legs, and clean and grease it every time the bike is used, if it is badly worn then a new distance piece may have to be machined up, check out of round of the frame head-stock first.
If the legs of the H piece are parallel in both planes , sometimes you can get a tight spot out of the H piece using a suitable mandrel driven into it , carefully, or a slotted rod and abrasive cloth, first work out where the tight spot is and concentrate efforts there.
Foss