adyv8,
I assume the rockers you have are the ones that look like an exact copy of the std AL ones - except in steel? (not actually steel of course, but Cast Iron). If one has worn and the others haven't, the most likely cause is that the surface hardening treatment on that one is not correct. This assumes of course that there is nothing strange about the top of that one valve stem compared to the rest.
Get it replaced FOC.
Russ
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