Music library from Music app disappears at EVERY restart, no matter what

As in the title. After the update to Sonoma (currently on Sonoma 14.2 on a 14 inch MBP 2021 with M1 pro) the Music app has started to behave horribly weird. I am used to have a music library formed by a bunch of mp3 local files I have on my computer. After every restart, the files are still untouched on my computer but the library is gone in the Music app (so basically nothing shows in it). Which means that I lose, for example, all playlists I could create.

I have tried to re-import the files in all possible ways: from different origin folders, changing the music media folder location, with and without copying the files to the music media folder while importing the library... nothing. Every time that I restart, the library is gone. And, after the restart, I see a "Media" folder in my bin, that I never deleted.

If it may help: I don't have a Apple Music subscription... I am used to use the Music app just as a player for my local files.

Please I am desperate!