"Luck" should not be a word in the engineer's vocabulary %-B. There is no such thing as "bad luck", there is only bad design. Of course you can hit a defective component and that can be called bad luck, but to design on purpose on the edge of tolerances is not luck, it is a recipe for eventual failure. And a needless one as well established methods exist to estimate and evaluate impact of tolerance variations on the design. But then, not everyone bothers. And of course in these days of planned obsolescence sometimes failure is the design target.
Of course it all depends. Buy a bargain gizmo from DX and you are guaranteed to get "luck" in the deal - usually the bad kind. Design something like the primary coolant circuit or fuel rod manipulators for a nuclear reactor and the word "luck" is one you hear seldom if at all.