717 Valve Problem

[Ronno6]

Got an interesting valve problem with a 717.
The valve seems to hang open and does not close when cocked.

I rave replaced the valve 3x now with brand new Daisy valves , and lubed the stem on each.
The problem persists.
It usta wold hafta be cocked and snapped once before the valve would seal when cocked, but that doesn't work any more.

Any ideas??