The cause of this failure is due to one of the following reasons. A leaking engine rear main seal. A leaking internal hydraulic slave cylinder. Over greasing of the front bearing retainer quill on the transmission. Many times we see wear on the clutch disc on the outside edges only.
Common complaints are slippage, chatter or non release.
Failure to resurface the flywheel. Flywheels after extended usage will concave on the outer edges of the contact area thus reducing the contact area. If this happens, the entire weight of the transmission is supported by the very thin cushion segment of the disc. It is not designed to support that weight. The clutch disc will now wobble on the input shaft.