Grabby clutch, S4R

This is a better place to put this enquiry, rather than the Random Chat heading.

My new-to-me S4R has a grabby clutch for no obvious reason, since the plates all look OK. Possibly it doesn't have the belleville plate in it: I didn't check. Has anyone experienced this and cured it? I could just buy a new Barnett clutch pack, the best I've experienced, or even try doping the plates with lithium grease as I've seen suggested elsewhere, but that must cause clutch slip, surely?

Nick