As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE IT WAS OBSERVED CABIN ALTITUDE TO BE FREQUENTLY OSCILLATING BETWEEN 500 FPM RATE OF CLIMB AND 300 FPM RATE OF DESCENT. REMOVED AND REPLACED NR 1 CABIN PRESSURE CONTROLLER IAW AMM 21 31 01 AND OPS CHECK GOOD IAW AMM 21 31 00 700 802.