Is Correcting a Crooked Nose a Difficult Procedure?

Because I know at least 2 incidents that the surgery was unsuccessful and their nose is still crooked and they have a hump in one side. What I wanna know is why is this difficult to achieve ?Is it because the crooked nasal bones aren't too much mobile or the blame is on the surgeon ? Which procedure would you classify as more difficult, straighten a crooked nose or a typical rhino (aka hump removal and correcting of the open roof) ?