I can verify your research - replacing the "i" with an "h" makes it work like it used to. (Unfortunately, at least with the editor I was using, it made some of the other metadata get blown away, but at least the track volumes were now properly set from ReplyAlbumGain.) As I stated in another thread, something must've changed around Feb 2017. All my files from before then preprocessed with MP3tag and the $rg2sc() function have the "h" and the volumes are correct. All after that have the "i" and iTunes is not using the tag for the volumes. Could have something to do with the ID3 version (though all mine are ID3v2.3) or the way the frames are implemented or something. Someone who knows more about this stuff than me would need to look at it, but something changed and it's not right.