As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOTS REPORT VIBRATION SOUND COMING FROM BESIDE FO ON RIGHT SIDE OF AIRCRAFT UPON AC PULLING UP TO THE GATE, EXTERNAL POWER DOOR WAS FOUND UNSECURED DOOR CLOSED REF AMM 52-49-02. OK FOR FLIGHT OPS AT THIS OPEN. NO DAMAGE TO DOOR OR SURROUNDING AIRCRAFT AREA. LATCHES TIME SECURE TIGHTLY ON EXT POWER DOOR, LIKELY LEFT OPEN AT PREVIOUS STATION. DID NOT FIND ANY OTHER DEFECTS TO CAUSE VIBRATION.