As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MAIN CABIN DOOR AT ALT WAS MAKING A VERY LOUD SOUND CAUSING A RETURN TO FIELD. (FLIGHT 2953 - FILED CLOSED) FOUND LOWER FRWD. CORNER ON PAX DOOR SEAL TORN AND NOT SECURED TO DOOR SEAL TRACK. REMOVED AND REPLACED PAX DOOR SEAL WITH SERVICEABLE UNIT. PRESSURIZED A/C WITH NO ABNORMAL SOUND. A/C PRESSURIZED NORMALLY. REF. AMM.21-31-00, 52-11-07