Do any aircraft have an actual "freefall" backup? Are the hydraulic actuators disconnected from the MLG in such a design?
If not, the gear wouldn't drop if the actuator was unable to both push oil out in one end, and draw oil in on the other end...
That's what valves are for, and if valves fail or gets blocked...
Well... That's what started this thread, isn't it...?
An actual freefall design would probably prevent all three accidents, as the MLG did freefall on the first two accidents, but it didn't lock..