I know this thread has been on here a lot m3 slow reg refresh what fixed most of them restacking washers in a different configuration I have about 25 to 30 bar difference between them and 2 and reg is taking 30 seconds to refresh
If it's adjusted very close to its absolute maximum setting, the washer stack is very nearly squeezed flat which means the seat can't open.
Otherwise it's likely a symptom of the seat wearing over time. Can try replacing the seat or dressing it flat and smooth. Or if you're so inclined, upgrade it to a harder-wearing material like PEEK.
I just installed new peek seats in them rear reg is set to 153 is where it settled in at and not creeping unless I'm not a 100 percent flat when I polished it up idk
I have three M3’s and the one still has the stock pistons in it. I’ve never had refresh issues with any of the guns. Stock pistons or not. Never changed washer stacks or anything. I go with a 45b differential on all my guns.