Saxappeal I sent you an email but to keep this thread up to date:
The crash is related to the audio file scheduled for playback. This file seems to have an invalid file length or some kind of corruption that leads to an invalid file length.
Open the Files app, and rename the file that Stage Traxx tries to load (you should see the name briefly before the crash) so that Stage Traxx can no longer load it. That will get rid of the crash.