Xcode console message: [default] RETURNING UnknownFS

Wow, that’s an obscure log message. This is coming out of Icon Services, which logs this message when it’s unable to find the icon for an item and, furthermore, that item doesn’t fall into one of the common fallback categories (app, folder, data). I’ve no idea why you’re seeing, but it’s unlikely to be an indication of major problems.

If you find it super annoying then I recommend you file, making such to include a sysdiagnose log [1] taken shortly after seeing the problem.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

[1] See the instructions on our Bug Reporting > Profiles and Logs page.