Does it change at all if you cycle the trigger quickly? I changed my electric valve out after a few years use on my 135 for that same reason. Cycling it quickly with the trigger a few times would make it stop leaking.
I also changed the regulator at the bottle when it decided to pass too much pressure and push past the trigger valve. I'd change out the trigger valve first (cheaper) unless your local shop has another regulator you could swap out just to see if that is the cause.
I'd like to hear the outcome when you find it …