There not a tight fit. The shaft wears more than rocker bores. On Vitesse, my shaft was worn (more so at the front), so the oil scrolls/grooves no longer existed. No noise and didn't affect valve clearance, though oil not lubing the rocker bores/valve tips and maybe the cam, if not running down the push rod holes. You should be able to see oil running in this area when idling, though if not could also be blockage in shaft/rocker oil holes.
I just changed the shaft as, cheap (though maybe crap), as also the re manufactured rockers could well be crap.
Dave