As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE OUT OF SERVICE IN HEAVY CHECK, MAINTENANCE FOUND AFT CABIN FLOORBEAM UPPER WEB CORRODED BETWEEN FR87 AND FR88 RBL 12 TO 42. MAINTENANCE REMOVED AND REPLACED FLOOR WEB AT FR87 AND FR88 IAW SRM 51-40-08. THIS AIRCRAFT REMAINS OUT OF SERVICE FOR DURATION OF THE HEAVY CHECK COMPLETION.