Hard to say what is happening but on the 1st pic a small black spot on the left side should be related to a specific spot on the sleeve. As mentioned by me in that R2104 topic, in the past it was normal to remove all sharp edges of the ports and I think that still will help today. About the spot over the whole side, a friend who worked at a metal company said such spots look like a cold welding. A moment that the pinch and temperature was high and the lubrication too low. Still I do not rule out that the rough edges of the ports can be the cause.