Bold lines or a sub-heading I put right under the chapter title disappear in the PDF. What's wrong?

This was a bug, fixed in version 1.9.3. When preparing a book for export, BookyAI removes the chapter title if the AI repeated it at the top of the chapter, and that rule was too broad: it also removed any bold line or sub-heading sitting directly under the title. Only a genuine repeat of the title is removed now. Update and export again; nothing needs to change in your text.