As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MCN - DURING C20 CHECK DISCOVERED CORROSION ON THE AFT CARGO DOOR SILL WEB FROM BS 794 TO BS 847 AND STR 25R. CORROSION WAS FOUND TO BE OUT OF LIMITS IAW BOEING 737-300 SRM 53-60-15-1A1 FIG 101. MAINTENANCE REMOVED WEB AND INSTALLED NEW WEB FROM BS 794 TO BS 847 AND STR 25R IAW BOEING 737-300 SRM 51-40-02-0G.