[Fela]

Apparently the song name guessing algorithm got changed recently to insert space in front of capital letters?

That change in itself is actually quite welcome, but there should be a way to retroactively use it on already generated song titles.
It's creating havoc with duplicate songs otherwise, as duplicates are apparently judged based on the song name, not on the file name.

[Zubersoft]

The avoid duplicate songs feature does use the full file path, not the song name. However, the default storage setting of "Use Subdirectory per Song" uses the song title as the folder name, so naturally this affects the duplicate file detection. My advice would be to back up your library, then restore that backup file (which will move all of the files into the appropriately named directories), so that the avoid duplicate songs feature works from that point onward.

[Fela]

The avoid duplicate songs feature does use the full file path, not the song name. However, the default storage setting of "Use Subdirectory per Song" uses the song title as the folder name, so naturally this affects the duplicate file detection.  My advice would be to back up your library, then restore that backup file (which will move all of the files into the appropriately named directories), so that the avoid duplicate songs feature works from that point onward.

Restoring the Backup won't rename the songs to the much nicer interspaced names though, will it?
(Still considering that on my primary tablet for the annotations...)

[Zubersoft]

Sorry, I somehow got the idea in my head that the restore might fix the directory names, but it would use the existing song titles, so that wouldn't really work. If you turned off the "Create Subdirectory per Song" option before restoring the library (and don't restore the settings from the backup), then this would fix the problem going forward.