4L80E - Excessive Direct Drum Wear

This is a home-built, late-case (02'), unit with a CK brake, a number of upgraded hard parts, and its dual-fed along with typical lube mods. The entire unit had been torn down and inspected and the only real odd issue I came across was excessive wear on the direct drum from the 4th (bottom most) center support sealing ring. The 1st and 3rd ring areas show some typical polishing, but the wear is immeasurable. This 4th ring, however, shows significant grooving and wear that I have never seen before on its own.



The clutches/steels throughout the unit, and the directs, are all like new. And the sprag itself, and its journal, are also in perfect health. I am planning on mending the drum with a Sonnax sleeve kit (34838-01K), as being a 36 element drum it makes fiscal sense too, but I want to make sure this doesn't happen again.
Is there any specific cause that could have accelerated this wear? And what would need to do in order to prevent this from happening again? The unit had plastic style sealing rings on the center support, that I have never had a problem with, and a press fit sungear shaft, that was confirmed concentric to the drum after installation.
The only wear is the bottom land from the center support, the others barely even polished the surface.
The drum is already machined and I am awaiting delivery of the sleeve kit.












