Thanks, John(UK). I did replace with a new valve but my concern is if the aftermarket internet valves are the quality of OEMs; they’re much less expensive.
I know the oil in the valve was very clean and there was no foreign material holding it open. I also know it was not the check valve as there was relief valve frothing in testing and the bench test showed leaking at <100 psi.
As mentioned, I suspect the valve stem was binding in the spring compression nut (probably from lack of activation) which resulted in the stem protruding .022” beyond the nut.