What was found
AIRCRAFT WAS NOT GROUNDED: ON ROTATION OUT OF LAX THERE WAS A VIBRATION AS THE NOSE WHEEL LEFT THE GROUND WHICH CAUSED THE COCKPIT DOOR TO FLY OPEN, NO LOCK FAIL ANNUNCIATION. THE FLIGHT ATTENDANTS WERE ABLE TO CLOSE IT ON CLIMB OUT AND IT STAYED CLOSED AND LOCKED. LEAVING MEX THE SAME SCENARIO OCCURRED. BOTH ENROUTE TO MEX AND ON THE GROUND IN MEX WE CHECKED THE DOOR LOCK AND IT OPERATED NORMALLY. MAINTENANCE FOUND LATCH BROKEN ON ELECTRIC STRIKE SIDE. REPLACED LATCH IAW AMM 52-51-03.