As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK, FWD SERVICE DOOR FAILED TO SEAL AROUND UPPER SECTION. DOOR WARNING LIGHT WOULD NOT TURN ON WITH DOOR OPENED. OPERATED AND INSPECTED DOOR. NO DEFECT NOTED, OPS CK GOOD. DEFERRED DOOR WARNING LIGHT, LATER AT SLC REMOVED AND REPLACED DOOR PROX SENSOR SPRING PER MM.