Just recreated this issue. The GUI closed when I dragged the File Reader into the Signal Chain while the sound source was set to bluetooth headphones. This did not happen with wired headphones.

activity_bluetooth headphones_file reader.log
activity_wired headphones_file reader.log

Thanks, this is super helpful! It's almost certainly crashing here, when trying to create the File Reader buffers based on the audio device settings.

The bluetooth headphones may not have a standard sample rate (at least the ones I just tested don't). We can add some checks to make sure the sample rate is valid before creating these buffers.

Just so you are aware, my bluetooth headphones did not cause this issue. Let me know if you need me to troubleshoot anything.