Stuck adding music to library, some tracks still lack to be identified [Solved]

Thank you @vova.

I fixed it using a backup.
Probably something wrong with the database during the migration from OSX to WIN10 as you stated.

Also (but not related) it is important to change the library path syntax after the database migration.
See: OSX to WIN10 migration issue: Truncated NAS library path? [SOLVED]?