CO2 system - is this normal?

My Ultralife CO2 system has required frequent adjustments since the day I
first installed it.  With a full tank, I open the little "needle" valve
fully, then turn the knob on the regulator/valve set clockwise until I see
about 10 bubbles/second in the bubble counter.  I then close the "needle"
valve until I get about 3 bubbles/second.  This continues for anywhere from
one to ten minutes, then the bubbles cease.

I repeat the process, and it goes a little longer before stopping; maybe 5
to 15 minutes.  Eventually, after much putzing, the system runs for  a few
days without needing re-adjustment.  This happens regardless of whether or
not I have the pH controller and solenoid installed.

I'm assuming this isn't normal, but could use help in figuring out what the
problem is.

I sent the regulator, controller and solenoid back to Ultralife because of
this and possibly a related problem: after a week or two, the system blasts
CO2 like gangbusters for no apparent reason (no adjustments had been made
recently).  They supposedly ran it for two weeks, but their only
observations were that the regulator was set much too high and that I was
obviously an idiot. (FWIW, they also sold me a new pH probe, because the
original, after 8 months, would no longer register under 14.3.
Unfortunately, the "new" one won't read  above -3.5, so I'll be doing
without the controller for a while.)

Thanks in advance for any insights you can offer.