Audio volume stream never released

I’ve been using Monogame+Cocos2d-xna for my game Arcane Quest 2.
Everything works fine, except that the game takes control of the Music volume stream and never release it unless you force kill the game.
Basically once I start the game, the hardware buttons control the “music” volume. Once I exit the game (it’s still running in background, I understand there’s no way to actually kill the game), the hardware buttons still control the music volume, and never return to control the ringer volume,

Any solution?