Frans
You need to refer to the strata plan inthe first instance. If the gate and fence are delineated by a thick line and shows thst it’s the boundary between common property and your lot, then the gate is common property . It’s like it was a wall. In this case it’s the OC responsibility.
You then need to refer to the bylaws. There may be an exclusive use bylaw transferring the upkeep of the gate to the lot owner.
The OC may argue that the lock was not part of the original building. Let them prove thst point.