Playing as the Kapaku, I have had many instances of battle music persisting after the battle has ended. This is resolved by a save/reload.

Here's what I have noticed so far:

• It seems to only happen during Dust Eclipses

Will do more situational testing.

Edit: Just had it happen without a Conflux bonus while fighting a quest mob (second mouse). I've had it happen while fighting another faction (necrophage; at war). I've also had it happen while fighting a roaming army. All seem to happen during Dust Eclipses though.