Maybe I'm wrong, but it looks to me like when the ring was initially parted off there were some very small irregular tears in the maple wood fibers around the edge of the ring(this leaves small irregular valleys at the edge). We all pick up the parted rings and run our fingers around the edge to remove any lite burrs (loose fibers on the edge). The other ring appears much more cleanly cut (fewer valleys). When glue is applied, while mating the butt sleeve, some fills these valleys and when sanded show the discoloration common with excess epoxy at ring interfaces. It may have a very small amount of ebony dust that got smeared in but I really doubt it. Dust would have appeared on the other ring also, but it doesn't appear to be there from my view.
The only suggestion I have is double and triple check all surfaces and edges with a strong magnifying lens BEFORE applying any adhesive. It's surprising what you will see. Correct these imperfections and definitely wipe down and blow off surfaces to remove dusts BEFORE gluing.
Just my 2 cents. Take it for what it's worth.
Tom Gedris, Triple Cross Cues