"Load lyrics beside music file" not working

[porg]

Prerequisites

• LyricsX → Preferences → General
  • Preferred music player: iTunes (Note: called Apple Music for a while now)
  • Lyrics saving path: LyricsX (Default) which lives at ~/Music/LyricsX/
  • Load lyrics beside music file: ON
  • Keep Music Media folder organised: ON
• Apple Music → Files → Music Media folder location
  • I do not use the standard location!
  • But I use a custom location: /Volumes/my-music/Shared/Music/Media/Music which I refer to as `MusicRoot'
  • Note: Maybe that custom media library location is the cause or at least related to the bug?
• At MusicRoot I have the following folder/audio-file structure (managed by Apple Music) with .LYR files added by another app than LyricsX and some self-created lyrics files.
  • Artist A
    • Album X
      • 01 Song One.mp3
      • 01 Song One.lyr
      • 02 Song Two.mp3
      • 02 Song Two.lyr
      • ...
  • Artist B
    • Album Y
      • 01 Song Uno.mp3
      • 01 Song Uno.lyr
      • 02 Song Duo.mp3
      • 02 Song Duo.lyr
      • ...

Reproduction

• Start to play a song which has a music file and a lyrics file besides it (aka sidecar file) in the filesystem.
  • Expected: The corresponding Lyrics show in the Karaoke Lyrics overlay which I have activated.
  • Actual: No lyrics are shown.

Further Experimentation

• I open the Lyrics Window, which says: "No Lyrics. Drag & Drop to import LRC file"
  • I drag and drop the LRC file manually from Finder and from now on the synchronized lyrics show just fine.
  • After playback of the current song is stopped, a corresponding .LYRX file gets copied to ~/Music/LyricsX/.
  • It's a duplicate. Almost. Only difference I noted: The original LYR has centiseconds (.000) and the created LYRX has milliseconds (.000).
• A also did the Reproduction again with a new song with the Internet connection off, so rule out a conflict of the automatic internet lyrics lookup vs. the local sidecar file lookup.
  • Made no difference. Same problem

Suspicions

• Your app has some hardcoded filepaths which are troubled with a custom media library location.
• File access permission issues? If so, what would I need to grant and where?