As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MAIN CARGO DOOR LIGHT ILLUMINATED WHILE LEVELING AT FL 290. CABIN PRESSURE WAS VERIFIED AT 8.0 PSID & NO OTHER INDICATION OF AN OPENED DOORS NOTED. FOLLOWED ORH PROCEDURES AND RETURNED TO MIA. REMOVED AND REPLACED S9033, ADJUSTED AND TESTED IAW MM 52-70-009-5. MCD OK FOR SERVICE.