As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION TYPE:NA**SUPPLEMENTAL SDR** AIR TURN BACK DUE TO LOWER FWD CARGO DOOR OPEN INDICATION JUST AFTER TAKEOFF. BOTH ECAM AND SYSTEM PAGE CONFIRMED DOOR OPEN CABIN ALT COULD NOT BE VERIFIED DUE TO PHASE OF FLIGHT. DEFERRED CARGO DOOR INDICATION PER MEL 52-71-01-2. DMP COMPLIED WITH. VERIFIED LWR FWD CARGO DOOR CLOSED. PLACARD INSTALLEDREPLACED SWITCH 16WS PER MM 52-71-00, OPS CK GOOD. THIS CLEARS M771857. PLACARD REMOVED.