By no means am I an expert and I am sure one will be along shortly. A thought occurred to me though, if you are using a GLA inline diffuser, I think that you need at least 30 PSI to force the CO2 through the ceramic. It could be that as you increase the pressure, it just builds up between the regulator and the diffuser until it is equal to what you have set. I can see the bubbles in the counter stopping then. Then you increase pressure and it goes again until the pressure builds back up to the new pressure setting and stops. Just a thought.