As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SUPPLEMENTAL CLIMBING THROUGH FL280 CABIN ALT WAS AT 8900. SHORTLY WENT INTO THE RED RANGE AND POST A CABIN ALT OF 10000 FT. DESCENDED AND CABIN PRESSURE APPEARED TO RETURN TO NORMAL. DEFERRED PRESSURIZATION SYSTEM AUTOMATIC AND MANUAL MODE. M PROCEDURES C/W AUTH 020281DM-C REF 21-19. REACTIVATED SYSTEM IAW AMM 21-31-03-440-801-A. REMOVED AND REPLACED ELECTROPNEUMATIC OUTFLOW VALVE OPS CHECK GOOD IAW AMM 21-31-00 MEL RESTORED.