Oddly the problem seemed to go away... self adjustment by the clever machine? I think original problem was from me impatiently pumping too fast and bending something. Anyway using my new paintball setup seems to slow down the pumping response even more.
So my new approach is to just hold the lever down till it buzzes (= overpressure valve) or better yet just beforehand. I am sure this is a "bad thing", and reduces co2 absorption as the bubbles just follow a stream back above the surface instead of hitting undisturbed water first. But I think my paintball setup isn't as good in penetrating the water fast and downward anyway.
What I do next should help... which is to leave the cold, carbed water on the sodastream machine to reabsorb from the gas pocket, while I fuss with setting up and opening flavor ingredients. Hopefully then I don't blow off much more wasted co2 by saving these umpteen tedious pumps.
Tripping on carbonic acid, high on fructose!