Follow the linkage.. I think you'll find some fiber disks that "squeeze" it.. just tighten the screw or get new disks.
BUT just tightening the screw normally takes care of the problem.
Kubotas B2710, M6800, L6060 cab, Volvo EC excavator, 2 ZTRs and various implements.
Do not know the linkage here but as has been told most likely the design but may have a nut with locking built in that needs to be replaced or a cotter in that needs to be removed and could be missing.