As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT THERE WAS A VERY LOUD SQUEAL COMING FROM THE LEFT ENTRY DOOR. PERFORMED GVI OF L1 DOOR SEAL, SEAL RETAINER AND THRESHOLD WITH NO DEFECTS OR DEBRIS NOTED, REF AMM 52-09-01-6. CLEANED DOOR SEAL AND SEAL FAIRING SURFACE, REF SAME. SUSPECT DOOR SEAL WAS NOT FULLY MATED WHEN CLOSED PRIOR TO DEPARTURE. NO HISTORY FOR THIS ITEM. OK TO CONTINUE.