How does al-Nawawī explain the extra “bna” in the Al-Bushra wording of report 92?

The Necessity and Boundaries of Narrator Criticism

• It establishes a separate criticized narrator named Yaḥyā b. Mūsā b. Dīnār
• It is an accurate genealogical addition and Mūsā b. Dīnār is not the subject
• It is an extra textual error; Yaḥyā al-Qaṭṭān is the critic, Mūsā b. Dīnār the subject of criticism
• It records Yaḥyā al-Qaṭṭān criticizing himself