I found that even with worn plates with my Plunger A10 clutch. Main thing was that when doing spring adjustment, the spring nuts didn't turn on far enough to have enough preload, and tended to undo themselves
I remedied it by leaving out at least a friction plate, and maybe a steel also (I figure leaving a steel on steel won't matter as they spin together).
I've since replaced the friction plates, and only added in four of the five and don't have a problem other than I need to add some preload to stop minor slipping. I'm figuring on swapping the extra one in/used out periodically, just to use it.