As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE INSTALLING TAIL BOOM WHEN COMING UP TO REQUIRED TORQUE ON UPPER RT TAIL BOOM TO FUSELAGE ATTACHMENT BOLT PN NAS 628, A 'POP' NOISE WAS HEARD AND THE BOLT THREADS SEEMED TO BE STRIPPED. THE BOLT AND NUT WERE REMOVED AND THE NUT WAS FOUND SPLIT IN TWO PIECES. CAUSE UNKNOWN.