As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT WING RIB 5 FITTING INBOARD REAR SPAR FASTENER 4 FROM THE TOP, NUT SHEARED OFF. BOLT LIKELY SHEARED AT THE TIME OF INSTALLATION. NO DAMAGE TO ADJACENT FASTENERS, FASTENER HOLES OR FITTING COMMON TO PROBLEM HOLE WAS NOTED INDICATING THAT SHEARING DID NOT OCCUR DUE TO OVERLOADING OF BOLT VIA GROUND OR FLIGHT LOADS. FASTENER WAS REPLACED WITH NEW OVERSIZE FASTENER AFTER ROUTINE ACCOMPLISHMENT OF COLD-WORKING.