As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE RETAINING RING DISLODGED FROM THE RETAINING RING GROVE, WHICH ALLOWED THE PISTON AND ROD AND MAIN GEAR ACTUATOR GLAND TO SEPARATE FROM THE MAIN GEAR ACTUATOR CYLINDER PREVENT HYDRAULIC PRESSURE FROM BUILDING WHICH IS NECESSARY TO OPEN THE MAIN.