A chapter repeated the same sentence over and over, or the whole chapter appeared twice. Is that fixed?

Yes, from version 1.9.22. Some AI models occasionally fall into a loop and write one sentence hundreds of times, or send a chapter twice. BookyAI now catches both: a text where a sentence comes back again and again is cut at the start of the loop and the chapter is asked for again, and a chapter received twice is kept only once. If an older chapter of yours has this problem, regenerate it from the book's page; its old text is kept in the chapter's Versions.