Whatever it is, it seems to have stripped the crankshaft gearing or something like that on my 999S at Brands on 4 July. Clearly, not just a case of the coil or spark plug failing.
The Garage informs me that a full engine strip is required and that they've never seen a case of it before. Covered under the warranty, thankfully.
If anyone has an explanation of what's happened in layman terms, I'll be delighted.
