It is all starting to make sense.....when tearing the engine down, the oiler nozzle should have been pointing toward the gap between the crank gear and cam gear. But it was not, instead pointing straight up in 12 o'clock position, so it was done wrong.
Therefore no oil was getting to the gear interface, and probably that same oil supply also feeds oil down to the cam gear/ thrust interface, which now was getting no oil.
The cascade was the relative motion of the cam gear to the thrust plate was not lubricated and therefore from the heat, the gear face wore away and the thrust gap grew and camshaft began to walk back and forth then damaging the back of cam and cam plug in the block
