As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MCN - MAJOR REPAIR - DURING C-18 CHECK CORROSION WAS FOUND ON AFT CARGO COMPARTMENT INTERCOSTAL AT RBL 21, BETWEEN BS 927 AND BS 947. MAINTENANCE REMOVED CORRODED INTERCOSTAL AT RBL 21, BS 927 TO BS 947; FABRICATED A NEW REPLACEMENT INTERCOSTAL PER DWG 69-35359; INSTALLED REPAIR PART IAW B737-300 SRM 51-40-02, FIG 8, PG 38.