check book when adding the audio, I noticed that the created F7 feature in editor gets errors from the piper m4a files created, book bug check seems to tell us, its not doing something right, please note my current calibre build under windows is 8.16.2, Add text-to-speech narration within the calibre editor has errors under check book (F7 key) here is the text is displaying, so its doing something wrong for both epub and kepub, maybe this is a new bug, or the add speech for calibre viewer has problems, the audio playback works right, but check book seems to think its not correctly applied I guess.
