I use a full "Float Coat" which probably uses the same or similar system.
On one occasion when I was about to jump into the pool to test, prior to
cleaning, I checked the system visually (it's covered under a flap) and
was surprised to see that the CO2 cylinder had become unscrewed from the
release ..... how, is beyond me, and I can think of all sorts of reasons
including "operator error".
Since I use this unit (wear, not immerse) almost on a daily basis,
checking the CO2 has become a much more frequent exercise.
Except for this one time, whenever I jump in for a "test", the unit has
worked as advertised.

otn