A possible bug (I think) is the fact that when a new audio book is added to a book collection, the audio file is added to the first book (that already has an audio file).
In the image below you can see I added a 4th book to the collection, but the audio file is added to the 1st book.
(NB, Of course this can be deleted and added manually again to the 4th book.)
Thank you for spotting this, @beenkhoorn. This has been fixed for the next version.
I ran into a similar issue in RAB. If I remember correctly, I think I realized that if I created the new audio-only book and skip adding the audio file using the “Add Books…” dialogue on the Books root, I could go back afterwards into the newly created book entry and add the audio file there without overwriting the audio from the first book. You might try that until the next version of SAB comes out, if the same workaround exists in SAB.
This issue has been fixed in Scripture App Builder 11.0.4. Thank you again for reporting it.