I have issue with genres in picard for some songs its updating alredy tagged songs with concatenated single string of genres instead of keeping it as multivalue
any suggestion how to prevent Picard from braking tags with multiple values?
What is the file format? In case of MP3 or other format using ID3 tags, what are the settings in Options > Tags > ID3?
Are the genres sourced from MusicBrainz or are you using some plugin? Or are these just the genres already present in the file?
Bit extreme late, but just in case some else stumbles on this:
Did you check Options - Metadata - Genres? Either unceck the use of the genres completely or check the link "Join multiple genres with: " and check if you have there a ; included and not an empty string or an /.
If you use something like the Wikidata Genre you should check there the "Genre Delimiter: " as well. Same thing.