After 18 months of getting buggered about by our flow controllers (two different makes), we just work without them now.
Flow controllers are over engineered, over priced, too sensitive, and not robust; they mess us about, they require good conditioned batteries, and they waste our time.
We just work with the pump now, you get a fast flow which is good if you like to work fast; rinsing is mega quick.
Try it, just wire you pump back up to the pressure switch (very simple to do; takes five minutes).