While tearing into my 468 for removal I pulled all the lifters and saw this on #2-cylinder.
I can't 'feel' the mark but I can see it.
My guess the Lifter stopped spinning...would you agree?
The cam lobe looks fine.
You can see the round halo from when it was spinning but who knows why it stopped...maybe a speck of hard debris between the two surfaces. I'm done with flat tappet cams