As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING HEAVY CHECK MAINTENANCE FOUND CENTER FUSELAGE III INTERNAL- CORROSION ON AFT DRAIN MAST INTERNAL AFT LATERAL STIFFENER BETWEEN FR 86-87; STR 28R-27R. REMOVED AND REPLACED AFT DRAIN MAST INTERNAL AFT LATERAL STIFFENER BETWEEN FR 86-87 STGR 27R-28R. REF EMB SRM 51-40-08. A/C REMAINS IN CHECK.