Yes, i have had this problem from the very start with the GP4000's, the first pair had long black threads that got wound around front and rear axles. I didn't see them for quite a while, I would have never suspected something like that could even happen. They might have interfered with the hubs spinning to some extent.
But Conti does not seem overly-concerned. I throw out their tires quite regularly when they get either frayed sidewalls like you describe, or deep tread cuts that distort the shape of the tire. I would think that with all the tires they have sold over the years, with these serious problems (I would call them defects) that someone would have been killed by now on a high speed descent because of a blowout. I'm sure it probably has happened, but I have not heard personally of anyone.