What was found
AIRCRAFT WAS GROUNDED: FLIGHT DECK DOOR WOULD NOT OPEN DURING LAVATORY BREAK FOR THE FLIGHT CREW. THE FLIGHT CREW REPORTED THAT THE UPPER LATCH THAT HELD THE DOOR CLOSED AND THE FLIGHT CREW MAY HAVE OVER-POWERED THE LATCH SYSTEM TRYING TO GET IT OPEN RESULTING IN THE LATCH HANDLE BECAME STUCK IN THE OPEN POSITION. THE FLIGHT CREW REPORTED THAT THE UPPER LATCH WAS MOVED BY HAND TO OPEN AND THE DOOR COULD BE LOCKED USING THE DEAD BOLT. MAINTENANCE REPLACED THE FLIGHT DECK DOOR LATCH MECHANISM AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 51-51-21.