As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: CABIN ALT WARNING DESCENDING THROUGH 26K. STAYED AT 10K CABIN ALT. NO MASKS DROPPED IN THE CABIN. FLIGHT DECK USED PILOTS O2 MASKS. ARFF WAS DISTPATCHED AS A PRECAUTION. AIRCRAFT LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED APU PNEUMATIC DUCT AT AFT PRESSURE BULKHEAD PER AM M 36-13-01.