As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: WHEN LEVEL AT F L270 #1 FLIGHT ATTENDANT REPORTED LOUD SQUEAL AT 1L WITH VIBRATION. WENT AWAY AS WE CONTINUED DECENT. MAINTENANCE PRESSURIZED AIRCRAFT AND NO NOISES WERE NOTED. MAINTENANCE FOUND THE L1 DOOR COVER PLATE LOOSE AND ACCOMPLISHED COVER PLATE PRELOAD ADJUSTMENT PER AMM 52-10-00-220-007-A.