Fox Rear shock valve core hissing

Hi guys. I tried adjusting pressure on my rear shock, and it takes air fine (doesn't hiss or leak while I am pumping), but then starts to hiss after I remove the shock pump.

I tried tightening the valve core with a valve core tool but that doesn't help. Took out the valve core and put a tiny amount of grease and retightened and that doesn't work.

Should I just buy a new valve core or is there something else going on here?

Would any valve for work? (Could I take one from another shrader valve to troubleshoot?) Or are they specialized for shocks specifically.