Well, my guess was right. The splines on the cam plate stripped. I don't think it was directly because of my shim though. The nut on the primary had loosened, allowing the cam plate and basically the whole primary move around. The cam plate shows signs of wearing against the nut and my shim, which was aluminum, was so thin that it was sharp and feel apart. I guess it's still my fault. I didn't use a torque wrench like I should have. The dealer may still cover it, because he told me I can do any mods I want as long as I don't submerge it and he'd still honor the warranty. I'll be driving right by the dealership tomorrow, so I'll stop by and talk to him. Since I already have it apart, I hope he'll just give me a plate to bring home.