Focusing ring looseness on 50/1.2 M-Hexanon

Question

Sorry, this is not a digital camera but an interchangeable lens for a Konica Hexar RF 35 mm film rangefinder camera. The focusing ring has about a 1/10 mm play or looseness but the optical unit within the focusing mount appears properly tight with no play. There are no external screws that can be tightened and removing the bayonet flange from the back of the lens reveals no obvious means of adjustment.