As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING SKIN PANEL REPLACEMENT IN AREA STRINGER END FITTING TIE BOLTS WERE REMOVED TO ACCESS FASTENERS THROUGH BS1183 FRAME FLANGE. TIE BOLT SHANKS CORRODED, FROM LIGHT TO SEVERE CORROSION. CORROSION NOT DETECTABLE WITH BOLTS INSTALLED. BOLTS REPLACED.