There is some ware in both pinions, but that didn't happen until the disc pinion started skipping, which I think was actually brought on by the failing cam, not the other way around.
My friend (as Providence would have it) had a whole knotter assembly that I just picked up. It's OLD and rusty, but the cam is good on it. I spent the better part of the night trying to get it off the shaft. I'll let the oil sit in and try again when I have some more time. If I can get it off of there, I should be good to go, at least until the next part breaks.