12:05 Garage- ’70 Duster build

So weirdly enough the pictures I'm seeing online don't look like there is any friction material. Does it just use the metal plates? Strange but technically possible. Not sure what that means for your root cause analysis. I'd maybe call Cass and ask. I've never had one of these apart.
I sent him an email. He says they are steel without any type of organic clutch material and should be generously coated with straight friction modifier during assembly. Mine do look pretty beat up. I ordered all the new parts from him today. As far as the failure analysis, maybe it's just 50 year old junk deciding to give up on life. His website says something about his parts being "heavy duty". Perhaps the original style had a weak point.