Book type of 'Audio only...' - app crashes but Book type of 'default' does not

Context : developing an audio only app (no text) using SAB v9.3 on a macOS Big Sur for non-literate people (majority of potential users) from a certain language group.

If Book type of ‘Audio only book (without text)’ is chosen, the resulting app frequently crashes or just won’t load at all with the message that it keeps closing. However, if the Book type of ‘default’ is used, the Audio only app works just fine and displays each chapter with the audio play buttons displayed at the bottom of the screen.

I associated each NT book with an SFM file (instead of a docx file) that will be associated with audio file/s depending on how many chapters there are for a book. Each SFM file for the book contains \pb for page break. This setup works for the Book type of ‘default’ but not for ‘Audio only book (without text).’.

Is this a SAB bug or is there something I’m missing when I use the Book type of ‘Audio Only book …’?

Thanks in advance.