If you make it far enough away from the car before your door closes, it won't lock.
If your passenger is the last one to close a door and you're already 10+ feet away, it won't lock.
But if you're in and out of the car a lot, say you're loading or unloading things, or you're cleaning the car, it gets annoying fast.
I stopped using it.
For those who do want to use it, it would help if Mazda keyed it to all of the doors and not just the driver's door.