In every car I've ever seen, if you don't close the door with sufficient force, the door gets into a weird semi-closed state. This state is invisible, which is why cars have various indicators and sounds to indicate it. But the lock mechanism is already in force, so in order to properly close it you need to open and close again, unlocking it (which is especially burdensome in case it's child-locked).
Is there a usability reason for this?
Is this just a mechanical limitation, and if so, why is it so hard to solve?