Bronze oil ring polishing out shaft / sleeve?

Hi all, recently I saw a case of pump thrust bearing high temperature and lube oil turning black in a between bearing pump. This uses oil ring lubrication (bronze oil ring placed on a carbon steel shaft sleeve) and the lube oil analysis shows presence of copper alloy particles, so it is evident the bronze oil ring has contaminated the oil. I try to swapped the oil rings between DE and NDE, it did not solve the high thrust bearing temperature issue. DE side radial bearing temperature has been good even before and after swapping the oil rings. The problem stopped recurring after we replace the thrust side oil ring sleeve and the oil ring with newly purchased parts from OEM.

Given that the oil ring is swapped but did not solve the problem (and no issue with DE side) but after replacing with new sleeve and ring the problem stops, i am thinking the problem lies in the oil ring sleeve itself. A visual comparison of the old vs new sleeve shows that the new sleeve has quite fresh machining marks, but the old one appears slightly polished. Now the leading hypothesis is that the long term slipping motion (~4 years in service) has caused surface finish of the sleeve to decrease, thus resulting lower frictional force between the sleeve and the ring, thus the ring is spinning slower and splash less oil towards thrust bearing.

Has anyone experienced bronze oil ring is able to polish the carbon steel sleeve or pump shaft? Typical understanding is bronze oil ring should be the one that wears and not the steel shaft or sleeve. Any similar experience is appreciated