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 UPPER AND LOWER SURFACE OF FLOORBEAM UPPER CHORD AT BS 344, BETWEEN RBL 12 AND LBL 50. MAINTENANCE REMOVED CORRODED SECTION OF FLOORBEAM UPPER CHORD AT BS 344, FROM RBL 12 TO LBL 50; FABRICATED A NEW REPLACEMENT SECTION OF UPPER CHORD, 2 EACH REPAIR ANGLES, A STIFFENER, AND SHIMS; INSTALLED REPAIR PARTS IAW B737-300 SRM 53-10-51 FIG 205.