Changed / Absent Music near the end of the game?

[Boon: White Toblerone]

I have recently completed the game for the first time, and recently, I've noticed a couple of quirks about the music of the game.

Firstly, non-combat music (Cities and overworld) seems to be absent - I can't pinpoint exactly when it went away, but I THINK it was around the time I finished Missed Beyond Measure. Also, the music comes back when I'm in loading screens, but blips back out when I load in. I can also confirm that going back to a far older save has the music present, and going to New Game Plus also fixes it, but loading back to my original save removes it again. It seems it's some sort of event flag that's causing it - Is this supposed to happen, and is there a way to get the music back if so?

Secondly, I went into New Game Plus but reloaded a save before that point, and since then, my title screen music has been different. Is there a way to change it back?