Pretty much as above.

My phone is an iPhone 11 Pro.

I went through & re-wrote all the tags to a large set of albums in iTunes, to make use of the way that foobar sorts albums. Which is to say that foobar sorts albums by title - as you'd expect - & I had previously used sort fields for this particular batch of albums, which foobar doesn't recognise.

Some of these albums were already on the phone & others were added as part of this recent sync.

Having finished the sync, all of the new albums are showing the new title, but the albums that were already on the phone have not updated at all & so are still sorted by the previous title.

I've tried going into the media library folder & re-scanning, but that doesn't fix it.

Anything else I can try before I re-sync to nothing & then put the entire library back on again?