Transitive verbs normally take object marking suffixes. However, the two verbs kwíyâ 'to not know' and də̀gî 'to refuse, not want', cannot take object suffixes (p. 98). A free pronoun must be used instead. Since, ordinarily, free pronouns are only used for subjects or topicalized NPs, the appearance of free pronouns in this context is exceptional.
Noonan, Michael. 1992. A grammar of Lango. Berlin: Mouton de Gruyter.