What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Narrative: while inflight operator checked brake pedal action and noticed brake pressure would not release. Operator landed aircraft on a grass strip while holding right rudder to compensate for the dragging left wheel. Just before the aircraft came to rest the aircraft nosed over, the propeller striking the ground, splintering the prop and the aircraft came to rest upside down on the canopy and vertical stabilizer. The aircraft was turned over and the left brake was bled. Inspection revealed the left master cylinder unused parking brake lever had moved to the closed position causing the brake lock up. Malfunction defect report submitted to inform operators that if this type of master cylinder is used, the parking brake lever must safetied to an open position to cause inadvertent actuation if the parking brake system is not used.
As the FAA filed it
NARRATIVE: WHILE INFLIGHT OPERATOR CHECKED BRAKE PEDAL ACTION AND NOTICED BRAKE PRESSURE WOULD NOT RELEASE. OPERATOR LANDED AIRCRAFT ON A GRASS STRIP WHILE HOLDING RIGHT RUDDER TO COMPENSATE FOR THE DRAGGING LEFT WHEEL. JUST BEFORE THE AIRCRAFT CAME TO REST THE AIRCRAFT NOSED OVER, THE PROPELLER STRIKING THE GROUND, SPLINTERING THE PROP AND THE AIRCRAFT CAME TO REST UPSIDE DOWN ON THE CANOPY AND VERTICAL STABILIZER. THE AIRCRAFT WAS TURNED OVER AND THE LEFT BRAKE WAS BLED. INSPECTION REVEALED THE LEFT MASTER CYLINDER UNUSED PARKING BRAKE LEVER HAD MOVED TO THE CLOSED POSITION CAUSING THE BRAKE LOCK UP. MALFUNCTION DEFECT REPORT SUBMITTED TO INFORM OPERATORS THAT IF THIS TYPE OF MASTER CYLINDER IS USED, THE PARKING BRAKE LEVER MUST SAFETIED TO AN OPEN POSITION TO CAUSE INADVERTENT ACTUATION IF THE PARKING BRAKE SYSTEM IS NOT USED.