What was found
(CAN) DURING CRUISE, DISCOVERED HANDLE FOR FLT DECK DOOR DEADBOLT MISSING & PILOTS WERE LOCKED IN THE COCKPIT. CREW LATER BELIEVED AIRCRAFT VIBRATION UNSCREWED HANDLE & IT FELL TO FLOOR. AN EFFORT TO UNHINGE DOOR MADE BY CAPTAIN & FLT ATTENDANT. CREW UNABLE TO RELEASE LOWER HINGES OR TO RESET ANY OF HINGES AS DOOR HAD POPPED OUT & JAMMED. UPON ARRIVAL, CAPTAIN CLIMBED OUT THROUGH EMERGENCY HATCH, MAINT CALLED OUT, DOOR REINSTALLED, ELECTRICAL PORTION OF DEADBOLT SYS DISABLED & SYS DEFERRED. UPON INVEST DISCOVERED 5 REPORTED CASES OF BENT/BROKEN DEADBOLT HANDLES. DUE TO FLT CREWS FORCING HANDLE. CREATED AN IN-HOUSE TASK 5250/01X FOR THE INSPECT CHECK OF THE EMERGENCY DOOR HINGE DISENGAGEMENT SYS.