Preliminarily, then, we can formulate negatively: There is no textual fault (and therefore must be no textual intervention) where one cannot decide between an authorial and an authorized third-person variant, even when there is merely ‘passive’ authorization of a textual departure (generally described as a printing error).
Following the definitions of Scheibe and Allemann (the latter yet to be discussed), we can now state as a criterion of the textual fault that it admits of no sense in relation to its context; or, with respect to recent literature, defies the specific logic, the internal textual structure, of the given text. The textual fault is an element in the text as documented and transmitted that is contradictory to the structure of the work in question.