When I download my audiobook files or build the single file, I get the old recordings instead of the ones I just re-rendered. Why?

Update to BookyAI version 1.9.12 or later. In earlier versions, when the order of sections changed between renders, the audiobook kept the previous MP3 files for sections that had not been re-rendered, and the single file was joined from those. Since 1.9.12 every render ends with a clean-up: any track file that no longer belongs to a section is deleted, so the audiobook folder and the single file only ever contain the current recordings. If you are already on 1.9.12 and something still looks old, click "Start fresh", render again, then "Re-build single file".