Gearbox clutch noise

The noise: Video

I've looked here and elsewhere and havent heard anyone else with this noise. I'm hoping has heard it and determined a cause. It occurs in neutral and appears clutch dependent. It also appears to occur in 1st and only 1st gear.

The engine made this noise occassionaly preceding a rebuild. Engine was rebuilt due to low oil pressure problem. It went down on power and would give low oil pressure warning when hot and ridden hard. There was no obvious cause of the oil pressure problem internally so I replaced both pumps, the over pressure components, seals and gaskets, rings, and other bits, and decked the head and valve cover surfaces to flat.

Motor internals are stock, motorex oil after every track weekend and oem filter every other. It is a track bike so there are a lot of other mods but just not where the noise is coming from, the bottom end of the engine.

-clutch has been checked and rechecked for proper assembly according to ktm repair manual

-pressure plate release bearing has been replaced

-it was unclear if the pressure plate/outermost friction disc should be offset one tooth from the rest of the clutch plates so I've tried both and no difference

-ive found no obvious signs of rubbing or grinding components or worn parts after a thorough inspection of the entire engine.