The heart of the mists
I don’t believe you can do anything about it on your end, though I think this isn’t necessarily a bad thing – sometimes you miss good songs if they get overwritten by stuff that’s non-specific (IE, the Christmas jumping puzzle music I would never hear, and that would be sad, if it were overwritten automatically by say, Ambient).
Some zones are like this. Crucible of Eternity and Citadel of Flames are notable examples that have their own, fixed, default BGM. Also holiday zones tend to, as well.