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-19 CHECK CORROSION WAS FOUND ON FLOORBEAM UPPER CHORD AT BS 328 BETWEEN RBL 12 AND RBL 52, WL 208. MAINTENANCE REMOVED CORRODED FLOORBEAM UPPER CHORD AT BS 328 FROM RBL 12 TO RBL 52, WL 208; FABRICATED A NEW REPLACEMENT FLOORBEAM UPPER CHORD; INSTALLED REPAIR PART IAW B737-300 SRM 53-10-51-2 FIG 205.