Joined: 21/08/2006 09:21:27
Could it be do with grouping field. SongKong can optionally add genre to grouping field as well as genre field, this is useful when you are using multiple genres because iTunes will only display the first genre ion the genre field, but the grouping field will show them as a comma separated list fo fields.
Using Grouping like this has been common practise for many years. But in 2017 Apple added support for works and movements (for Classical music) to iTunes, and for mp3 they repurposed the grouping field to be used for Work, (in contrast they created a new field for mp4), could this be the issue ?