I think kirrbby nailed it, the timing chain roller has been chewed to bits. Since it's polymer material, it hasn't scarred anything. And the absence of metallic particles would indicate that there wasn't enough timing chain whip to allow contact with the cylinder tunnel.
At this stage, I'd pull the stator assembly for a better look inside. You may be able to just remove the round cam cover and poke a finger into the cylinder tunnel; probably won't be able to really see it. I'm guessing that the tensioner piston cap, which is also polymer, is crunchy by now. There's also a plastic idler sprocket on the chain tensioner arm. If this were mine, I'd replace the roller, tensioner piston cap, idler sprocket and throw a new timing chain at it...peace-of-mind for an extra $18. While the stator is off and before you start ordering parts, inspect the oil pump drive sprocket. If the teeth look like new, you're good-to-go. If they're worn, replace that sprocket too...and inspect the oil pump internals. Worn oil pump sprocket teeth almost always indicate a binding oil pump.
FWIW, it's usually easier to R&R the timing chain roller from the bottom of the cylinder tunnel. Remove the tension arm, then the chain can be fished upward, into place, the roller going along (part way) for the ride.
BTW, if you lightly oil the new oil spinner cover gasket on the side that contacts the clutch face, leaving it clean & dry on the flange side, it will stick to the flange and release from the clutch next time you go the clean the oil spinner. You should be able to reuse it indefinitely thereafter.
One odd thing I noticed is that someone replaced the JIS screws with slotted heads. I've never seen M6 screws like this before.