Brian,

Its probably one of two things with used Cranes. Not knowing their actual "prior" life, hard to say, but most often it is as stated, a ( stretched or soft) adjuster screw, or perhaps a bad rocker. The Crane Golds after time would also tend to stretch ( normal wear and tear) the threads in the rocker boby. Basically just thread fatigue in the body). Those rockers would take a lot of abuse for what they are, but like anything, can wear . Check the threads real close on that rocker. Also as stated, make sure the rocker is getting proper oil ( check that pushrod length and rocker oil hole.

All that said, probably still a streched or soft adjuster and or rocker threads.

I should have some new spare rocker bodys in stock if its a 1.5 ratio.( Mopar Performance blue)

There may be some new " Crane style" rockers coming to the market, but I am not sure of exact schedule yet, hoping to know soon.