Remove the reg, inspect it. If it looks good, and all the orings look good with no even miniscule damage (look really close!) do this:
Get some 3M polishing paper (
https://amzn.to/486HJZe) and start from 1200 grit and work your way up to 8000 grit polishing in a circular motion the black delrin reg seat. You want it super smooth. Ernest Rowe has a video on this if you look on his Youtube channel. You can also polish the brass "nipple" that it seals against on the adjuster screw, but start with really high grit and make sure you don't leave any debris in there.
Then: Give it the special sauce! What is the "special sauce", you ask? Well, I'll tell ya.
Mix some silicone grease (
https://amzn.to/486tKmg) and a drop of silicone oil (
https://amzn.to/3sGE6ZI) between your fingers until it becomes a buttery slick concoction. Use it to lube every oring in that reg, as well as the brass piston shaft. Don't be shy, any overlubing will be blown out anyway, but do be reasonable still. This will help ensure your reg doesn't stick.
One last thing you can do is look at your belleville washers and make sure they are free from burrs, even giving them a little time on the polishing paper, as well if, you desire.
If you do those 3 things I can almost guarantee you will solve your problem. To me it sounds like you have a lack of lube or possibly bellevilles digging into your piston shaft (look for scratches/damage while you have it apart).
Hope that helps!
