As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT MADE PRECAUTIONARY LANDING SHORTLY AFTER TAKEOFF FROM BASE IN AIRPORT INFIELD DUE TO A SUDDEN ABNORMAL VIBRATION. UPON INSPECTING THE AIRCRAFT IT WAS DETERMINED THAT THE INPUT PINION/ROTOR BRAKE FLANGE NUT HAD BECOME LOOSE. FURTHER INSPECTION REVEALED THAT THERE WAS DAMAGE TO THE INPUT PINION THREADS OF THE MGB AND A REPLACEMENT WAS ORDERED. NO DAMAGE WAS FOUND AFT OF THE ROTOR BRAKE FLANGE.