Tags: not the same as local tags

I first tagged al my music in iTunes. Then added to Volumio. But there are more ‘genres’ than I had in iTunes. Checked some differences in another tag-manager. The tags I added in iTunes are shown up everywhere, except in Volumio. How is this possible? How are the tags generated and how can I change it?

Edit: I use Volumio 2 on the piano DAC

Updates made in iTunes don’t (always) get reflected back into the file. They only update iTune’s metadata.

To force a re-write of the Tags: File -> Convert -> Convert ID3 Tags.