At the point where failure follows. Also examining carefully — the same word for a danger and for the rigour that prevents it.
Greek κριτικώς (kritikos, able to judge, discerning), from κρίνειν (krinein, to judge, decide); at once the point where failure follows and the careful examination that exists to catch it beforehand.
At the point where failure follows if nothing changes. The same word names the careful examining that exists precisely to prevent that point from being reached unaware.