I have submitted a bug report ticket for this, but thought I'd put this up here as well in case someone has a solution or workaround. It's trivial enough so might not be something terribly obvious. It might even only be affecting me.
I recently decided to switch music tracks in my PQ in base PSO2, being the first time since NGS launched, and happened to notice that my copy of Eternal Encore (Xmas Edition) was playing the English version. I have Japanese audio set, and I know it used to play the Japanese track before the update whenever my cursor ran over the song.
Going through the normal troubleshooting routine, I did turn the game on and off again and it did not fix the problem. I then changed the audio to English, kept my distance from Afin, listened to the English track. Then switched language back to JP and checked again and it is still the English track.
I know not all songs will have dual audio, but this track is used by the in-game concert which does have dual language tracks. And I have occasionally put the song on to enjoy while idling in my quarters.
I hope this is only an oversight and not hard baked to only play the English version from now on and forever and ever.