One Step Forward One Step Back

All repairs tend to destroy the structure, to increase the entropy and disorder of the system. Less and less effort is spent on fixing orginal design flaws, more and more is spent on fixing flaws introduced by earlier fixes. As time passes, the system becomes less and less well ordered. Sooner or later the fixing ceases to gain any ground. Each forward step is matched by a backward one.

The Mythical Man Month, p. 122