I'd be surprised if you can find any trustworthy data on this issue. BMW must know of only a percentage of the afflicted bikes, because many owners, like myself, repair their bikes using the aftermarket upgrade +6mm clutch disk. 38,000 miles and a new clutch required. Bugs the shit out of me. I have been told that the issue stems from a manufacturing defect that resulted in misalignment between the engine and transmission. Judging from the looks of my OE clutch splines, I would say that is spot on. To my knowledge, the proper fix requires the front cover to be removed from the transmission and bolted to the engine. A dial indicator is affixed to the crankshaft and front cover runout is measured to determine the amount and direction of misalignment. Then, a machine shop is sourced to make some offset dowels that will correct the alignment. Front cover back on with new dowels in place to verify the repair, transmission reassembled, new clutch installed. Easy peasy. Shit. Of course an alternative is to replace the clutch disk and hope for the best. That's what I did this time. At 76,000 miles, I will have a choice to make, and by that time, input spline damage might require transmission disassembly anyway.