I believe it's a issue with the material the camshaft is made of.....I have torn them down, and noticed the metal starts to "flake" off the lobes in little peices, then it's only a matter of time. The cams also appear to be cast iron, not steel
Dang that sucks, so it's a matter of "when" not "if"... When I get the camshaft out of this engine I'm gonna look for that "flaking" of the lobes. Anyway it's not like I'm going to put another 50k miles on this thing once it's in my Duster lol, that would take a decade or more.