.....tighten the black knob more and it should stop leaking.
You probably have over tightened it resulting in the "needle" going through the hole of the delrin seal. I have made such mistake before. You may consider replacing that seal with spare that came with the Yong Heng. Normally the bleed valve does not require much force to get it closed.
Mine isn't a needle but rather a ball shape at the end of the screw. The hole in the Delrin is considerably smaller than the ball and does not go into or through the hole, at least in mine. I even swapped the black knob screws from the moisture bleed off side and both were identical in size and shape.
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