As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: CABIN PRESSURIZATION FLUCTUATES +700 VERTICAL SPEED FPM TO -700FPM IN BOTH SYSTEM 1 AND SYSTEM 2 INTERMITTENTLY DURING FLIGHT. REPLACED #1 CABIN PRESSURE CONTROLLER AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 21-31-34.