The pictures included are from a forty thousand mile - ish Brera engine. Clearly service shedules have not been maintained - oil levels allowed to drop, and or abuse of the throttle, low gears/high revs on fast bends - no sump baffles to prevent starvation. Plus Oil pick - up "Snout" is high above the sump pan floor.
First bearings to suffer are the front ones which I am informed is also common with the Busso. Reading a little more into this, it would appear when the Crankshaft is balanced it must include the front pulley/Harmonic Damper. However, it is borne out on two engines I have inspected - other bearings, although worn, were considerable less damaged than the front.
The three mesh screens across the VVT ports cause a pressure drop, slowing the VVT response. However, the oil feed to the inlet camshaft VVT is via the central screened port. Unfortunately the oil also feeds the front bearing caps of the
inlet camshaft. So oil travels up to the screen from the NRV below and circumvents the screen to proceed up to feed the bearing cap. In doing so, it also permits oil to bridge the three ports via the flats.
So not only can any contaminants - metal shards - get into the VVT advance/retard voids, it can also travel to the front bearing caps, scoring the camshaft and wrecking the front bearings and caps - blocking the oil feed to lubricate the cap which is a micro - channel that snakes acros the surface area of the camshaft.
The consequenses of all this, in the worst case is wrecked cylinder heads. My 112,000 mile 159 heads are worth only scrap value - whereas the Block is pristine, as if it came straight from production.