I also thought of my former "lover", who said he never lied to me. But he left things out, allowed me to believe the wrong things. But there was something else. I believe he wanted to tell the truth but found it difficult. I think he would have been relieved if somehow I had discerned it from his manner. He was lying but in a way not wanting to, not wanting to hurt me but also not wanting to bear the consequences of the truth.
The few times I saw him after our breakup he was more honest. He told me straight out that he had a disease he may have given me (he didn't; I was tested). I think he tries to be truthful but he engaged in various forms of prevarication for so long that it was difficult for him, and he allowed himself to slip into the easier role. I haven't come upon a section of Augustine's treatise that goes into allowing falsehoods to be believed while actually wanting the truth to be known. I suspect he could state it more elegantly than I am here.