There has been a consensus in the literature that pa- and pa-ka- can be traced back to Proto-Austronesian as the causative prefix of dynamic and stative verbs, respectively. This paper investigates an apparently aberrant use of pa-ka-found in Kaxabu Pazeh, where the causative affix freely alternates between its canonical usage as a prefix and an applicative-like free morpheme with a word order parallel to the ka-construction in Taiwanese Southern Min. With consistent evidence from Kaxabu causatives and ditransitives, I demonstrate that the unexpected restructuring of the affix can be straightforwardly accounted for as a contact-induced change driven by both phonological and structural triggers from the dominant language.