As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
YYC - FLIGHT 2331 - FLIGHT RETURNED TO FIELD WHEN AFTER TAKEOFF, THE CREW RECEIVED A FORWARD CARGO DOOR WARNING. MAINTENANCE INSPECTED THE DOOR AND FOUND THAT IT WAS SECURE. OPERATIONAL CHECKS WERE PERFORMED AND WERE ALL GOOD. MAINTENANCE WAS UNABLE TO DUPLICATE THE WRITE-UP. THE AIRCRAFT WAS RETURNED TO SERVICE.