this would be my thought as well.
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This was my exact thought, since the metal looks "soft". I used to do engine work, on 305's and such. I have yet to see this in real life, but I was told sometimes cams can not be hardened properly and cause longevity issues.

 

Wish i knew what caused it. Yeah, after looking for cams and at dyno charts for the 120R, almost no one seems to run them, since I could only find a handful. This was a second hand bike though, 1 owner prior to me. He loved this bike and dumped so much money into it, and bought it new on top of that. So, rather than motor swap, I want to keep it like he had it when he passed since this bike was his passion, and he had it setup exactly how he wanted it. Every little piece was thought out by him, and he spent big money on a part if it was hard to find.

 

Usually when the wear is on the nose of the cam it's the spring binding. Looking at the other lobe on the same cam it's showing some wear as well so it could be a soft cam, bad spring or a combination of both. I would inspect everything before reassembly.

 

I would look at the springs and check for coil bind also. There is probably a better choice of camshafts that would be easier on the valve train. Maybe talk to a reputable builder such as hillside or someone to help you pick a cam. Lifters, a lot of recommendations for Wfo Larry's lifters. I have a set waiting for me to pick a cam for my m8. Good luck getting it figured out and back together.

 

99C lifters?

 

Yup, Sifton shovel cams had a bad habit of cratering out like that.