Audacity is a free, easy-to-use, multi-track audio editor and recorder for Windows, Mac OS X, GNU/Linux and other operating systems. Assuming these files are normal and playable, this problem would be probably fixed by installing the FFmpeg Library. I've looked in the library folder and don't see anything related to audacity in the preferences folder or the library folder. Review the files you are going to delete and click on the Remove button to confirm the action.
Complete the removal of the Audacity app by emptying the Trash bin.
Audacity library preferences > PREFERENCES.
