As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ON DEPARTURE FROM AIRPORT, THE LEFT MAIN LANDING GEAR DOORS REMAINED OPEN. VISUALY CONFIRMED BY THE PURSER THAT THE LT GEAR DOORS WERE LEFT OPEN. CREW SELECTED GEAR DOWN AND LEFT GEAR DOORS CLOSED WHILE THE OTHER GEAR DOORS OPENED. CREW PERFORMED ALTERNATE EXTENSION OF THE MAIN LANDING GEAR AND RETURNED TO CYUL. MAINTENANCE INVESTIGATION REVEALED THAT WHEN THE LEFT GEAR DOOR CLOSED THE MAIN LANDING GEAR CAME DOWN DAMAGING THE LEFT MAIN OUTBOARD GEAR DOOR.