X15 overhead suprise

[ChickenHawk]

2350 x15, 348k miles, getting around to doing the first overhead adjustment. Found this little surprise waiting for me. Oil always changed at 15k, local work mostly interstate but some city driving. No damage to the roller, normal wear. Lobe for intake #1 just after the apex of the lift. Anyone ran into this before(edit: let me rephrase, is this the start of the signs of crankcase filter not allowing the pressure out, that I have read is common, atleast on the older versions)? Truck used to sit in winter time so some slight surface rust on engine brake rocker arms for front 4 cylinders. Valves were on tight side but not “out of spec” by Cummins standard. All the other lobes looked fine and rollers. Demandated but has been fixed.