TWO SCREWS THAT HOLD DETENT RAIL TO VALVE BODY CAN LOOSEN AND BACK OUT. ALSO, VALVE BODY CAN BREAK AT POINT WHERE DETENT RAIL ATTACHING SCREWS ARE THREADED INTO BODY.
DETENT RAIL WOULD BECOME FREE RESULTING IN PARKING BRAKECONTROL HANDLE JAMMING AND NOT RELEASING OR ENGAGING THE PARKING BRAKE.
REPLACE SUSPECT VALVE WITH IMPROVED VALVE.