As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FIRE BOTTLE GAUGE HAS INACCURATE INDICATION, FOUND TO INDICATE (0) ON PREFLIGHT. THE BOTTLE WAS REMOVED AND DETERMINED TO BE FULL OF AGENT AND NOTICED ROTATING THE BOTTLE MOVED THE PRESSURE GAUGE. BY HAND SHAKING THE BOTTLE THE PRESSURE INDICATION WOULD MOVE FROM A (0) INDICATION UP TO 800 PSI. THE BOTTLE WAS REPLACED WITH AN O/H UNIT.