Air Venturi 90CI air tank leak

My 90ci air venturi tank all of a sudden started leaking at the valve. Basically the ball bearing that's pushed against the opening with spring pressure is not resealing. Is there some sort of sealing washer that's supposed to be in here or does that ball make a seal against the inside of the opening by itself? I took it apart and cleaned it good and reassembled. I didn't see any type of sealing washer. After reassembling It leaked immediately under just 125 psi shop air.

This tank is less than 5 years old. Is there a way to fix this, and if not, any idea where I could get a replacement valve?

Thanks for the help.

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Van you clean and polish the seat and ball that tarnish ( looks like tarnishing) or a carbon build up my not allow a positive seating/ seal.. if stainless a little dab of barkeepers helper cleaner on a #2 pencle eraser pre formed to lightly scrub/ buff back to clean and shiney may do the trick..

Next maybe the spring fatigue not holding properly?..