Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Other / Unknown
Flight Crew Regained Aircraft Control
Aircraft
Arrived at ZZZ gate X after operating Aircraft X on the XXth of May (local date). Gate was clear and marshaling crew ready when we arrived. Parked normally and parking brake was set and 'set' light verified illuminated. Then directed my attention to overhead panel watching for external power to be connected. The parking break released and the aircraft rolled forward several feet before I was made aware the aircraft was moving. Stopped the aircraft again and tried to set the parking brake. Could feel the parking brake latch 'grab' when top of rudder pedals when depressed and parking brake handle pulled up but the brakes would not 'latch' all the way and hold the pedals. Several attempts were made to set the parking brake with no success. Aircraft was held stationary after initial movement by manually holding the brakes until a tug arrived and moved us back to the proper parking position and the chocks were in place. There was no injury to anyone on the ramp and no damage to the airplane. Parking brake would not fully engage.
B767-300 flight crew reported the parking brake failed after parking at gate.