Previous phonological studies have indicated that a sequence of dissimilar hetero-syllabic/morphemic vowels are dispreferred across languages because it creates vowel hiatus. As a result, it may engender multiple repair mechanisms. However, the repair mechanisms do not apply liberally; they may be resisted in certain positions when segmental deletion or featural change fail to take place. Segments in phonetically and psycholinguistically privileged positions invariably resist such repair strategies that may be quite regular in the grammar of the language. In this study, a reanalysis of data from Lubukusu language (Bantu, Kenya) shows that a Positional Faithfulness (PF) account within an Optimality Theory (OT) framework may be felicitous in explaining both the initiation and resistance to the said repair processes. The findings indicate that the positional faithfulness of the vowel in question may determine whether it is deleted or which features may be changed based on a single constraint hierarchy in an optimal grammar of the language. Preservation of lexical contrast in positions that are critical in language processing is accounted for through positional sensitive constraint domination.