App picks up wrong audio files

This is a problem that was solved before but now reoccurs. I have an app where the audio files of the different books are not uniquely named but have different sources (folders) on the server. The app is supposed to save them in different folders on the device that I define in Audio Sources, e.g.


However, just one folder is created with the app name (not with the name and subfolder that I defined in the Audio Source). Now if I go to another book and play the same chapter - let’s say chapter 1 - the app picks up my chapter file 001.mp3 from the device which is actually from another book. The same with streaming, when the file has been downloaded to the device before, even streaming doesn’t play the right file but it picks up the one that was saved before.