As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: THE CABIN ALTIMETER WAS CLIMBING AND DESENDING. SWITCHED TO SYSTEM #2 AND THE PRESSURIZATION STABLIZED AND FUNCTIONED NORMALY. REMOVED AND REPLACED CABIN PRESSURE CONTROLLER IAW AMM 21-31-34-000-001-A AND 21-34-400-001-A.