@ CROSSBOLT, you might be on the right track
@hawk, think it's very likely this camshaft. Are you chemically inclined?
- if yes, put some battery acid (few drops are enough) in two very clean flat bowls, glass, whatever
- try to get a piece of this camshaft off (oilfree) or around the camhaft there
- take a morsel (oilfree) from your shavings out of the oil (gloves and googles)
- both pieces should be appr. the same size
- drop them each into acid
- observe how they independently react, dissolve the same, boil up, or are completely resistent.....
Compare, with a magnifier, if it's the same reaction, you got your mizer.
It is a very rough test, but if your are very careful and precise with quantity of acid (gloves and googles) then you might see a result.
Take pics in several stages to watch then.
If I remember well, this (and many other brands) have been nitrated (heat-powder surface tungstened) and we had similar issues in the 90ies with this (very effective) hardening process on several machine parts.
I would assamble again and change the motoroil into a mix of thin sintethic oil and ATF (Automatic Transmission Fluid), fill, let the mot idle for a while, let it out, check, refill a new mix again, check.
Until no more specks of something are to be seen.
Then normal 10W40 Synt and go.