I swapped my reg out recently and after draining the airtube, swapping the reg and airing the gun back up I found that I had a slight leak from the bleed screw. I noticed that it took more force then usual to stop it from leaking. I bled the air back out and removed the bleed screw and tiny ball bearing to fimd a small sliver of aluminum on the sealing seat so removed it. Just filled thw gun back up and the screw took minimal force to seal.
Anyway, I think that when I bled the air I opened the screw too much so that there was room for the sliver of metal to get pushed under the ball bearing because I have drained the gun before and not had an issue (I assume the metal sliver has always been there).
If you need to drain your Leshiy I would only crack the bleed screw just enough for the air to start draining and be patient (unlike me)
that way if there is debris there maybe it wont have room to get onto the sealing surface and muck things up. If you do find that you have a leak there, dont crank on the bleed screw, it is better to take it out and clean it. If I had tried to tighten the screw too much Im sure I would have damaged the seat so it would never seal properly.
You can see the sliver of anodized alum. on the left from one of the threads somewhere maybe?
Anyway, I think that when I bled the air I opened the screw too much so that there was room for the sliver of metal to get pushed under the ball bearing because I have drained the gun before and not had an issue (I assume the metal sliver has always been there).
If you need to drain your Leshiy I would only crack the bleed screw just enough for the air to start draining and be patient (unlike me)

You can see the sliver of anodized alum. on the left from one of the threads somewhere maybe?