MrVideo, I tried with the second
.cue file you provided, and apparently it was imported just as expected, with all 21 tracks:
(since I don't have your original FLAC file, I simply used a dummy WAVE file of appropriate length, but otherwise the .cue file is totally unchanged)
Looks like the CUE sheet parser found all 21 tracks, and they all have a
positive length:
https://i.imgur.com/6zCbtGB.png
Also, all 21 tracks have been imported successfully, with all 21 imported files being
non-empty:
https://i.imgur.com/f82OBOg.png
Does importing that same .cue file look differently on your side? If so, can you please provide screenshots showing the same phases as above?