Is this the same problem the original 4449 had at initial release of the Kato GS-4 many years ago? Or is it a random issue with just the one unit you are reporting?
Like my initial post mentions (and also the A-board thread I posted the link to ), the problem appears to occur only on the locos which have decorated driver rims. It appears that Kato uses a different blackening process, just on those models. So it seems that the only affected GS-4s were the AFT (from the earlier run) and now the BNSF version (both locos have white-painted driver rims). The black/orange SP Daylight versions do not have the problem (from any run). None of those had that problem. I never owned the other (all-black) versions of this loco so I can't comment on those.
I wonder if you are thinking about the design flaw of the motor frame in the original run of GS-4 which caused DCC decoders to blow up. That was a totally different issue and that problem has been solved in the subsequent runs.
