What was found
PILOT REPORTED THAT THE CABIN ENTRANCE DOOR STOP WAS MISSING OR BROKEN. INVESTIGATION REVEALED THAT THE STOP HAD BECOME DISENGAGED FROM THE DOOR FRAME. THE AIRCRAFT HAS A HIGH NUMBER OF FLIGHT HOURS, AND THE STOP AND CHANNEL HAD BECOME WORN TO THE POINT THAT THEY SEPARATED. REPLACED STOP, AND REWORKED THE DOOR FRAME AREA TO ALLOW FOR PROPER ENGAGEMENT. SUGGEST PERIODIC REPLACEMENT OF THE DOOR STOP TO PRECLUDE SEPARATION DUE TO WEAR.