Ah, the music industry.
I know of one songwriter with multiple number 1 hits that was with a large american label for a while ... then moved to another, and the original label kept collecting the royalties when they were no longer contractually allowed to.
Their answer: "So sue us, it'll cost more than you'll get, we can drag this on for years, and you can't get costs awarded, so if we were you we'd just eat the L".