I believe the behavior of the app is such:
- You are working in folder /sdcard/Folder1
- Exit App
- Delete folder /sdcard/Folder1 using an outside app or event.
- Start App - it tries to set default to the now missing folder.
The same sort of thing happens if you change out SDCard and the path is not on both cards.
Adding a File exists check on preference read should solve this - and default to the other paths.
Thanks for the App!