RE: Blackbird Inlet Camshaft Failure - Why?

I Picked up a low mileage FI blackbird engine from ebay that's suffered a
very unusual failure.

The last journal on the inlet camshaft has been starved of oil and has
obviously chewed the camshaft and head. The engine was in the bike when it
failed and according the seller, wasn't involved in a crash.

It's a very unusual failure and I was wondering what would cause it.  Oil is
supplied to the camshafts from the cam chain end and fed through the centre
of the camshaft and out through exit holes on the lobes and journals. Being
furthest away from the oil feed it has failed where you would expect first
but the question is why?

The rest of the engine seems fine and once I pop a carbed head on it I plan
to fit it to the rarebird but I'd love to know why it failed in the first
place

Any thoughts?

JR