The Otari MTR-90 and similar rollers don't suffer from sticky shed, though it's a common supposition. The shed happens from the oxide face (the 'front') of the tape) and the rollers only see the BACK of the tape.
No, the problem with the Otari rollers appears to be some leeching into the material from the back of the tape. Under some non-scientific analysis, it appears to resemble some sort of carbon or graphite-like substance. This might make sense, since most manufacturers use some sort of dry light lubricant coating on the backing, to assist the pack in wind.
Anyhow, you're spot on in that when Otari rollers finally die, they go from being a functioning roller to something that's as useful as a chocolate teapot, stupendously fast! The replacement rollers like Athan corp products (and probably T-Reds and the like also) appear to be the sort of material that doesn't react with whatever the (presumed) lubricant is, and they can also be cleaned with alcohol without ANY deleterious effect that I've noticed.
There's a studio in Altamonte Springs right now that has a pair of A800s, one of which has a pinch roller that has dissolved in a very similar fashion: -Not something I see a lot of with Studers- and I have a replacement pinch roller here ready to go on it. -They never used alcohol in their rollers, and I'm actually wondering if the occasional alcohol cleaning wouldn't have done sone GOOD! -I mean, I suspect that a slight drying or de-oiling due to alcohol wouldn't have accelerated the problem, and might even have staved it off.
Keith