From the information you've provided, it seems like a component of the GNOME stack is at fault, not indicator-sound. So, I'm adding a task for gnome-settings-daemon, though I'm not sure if its to blame here (could be gnome-control-center or gnome-media)
From the information you've provided, it seems like a component of the GNOME stack is at fault, not indicator-sound. So, I'm adding a task for gnome-settings- daemon, though I'm not sure if its to blame here (could be gnome-control- center or gnome-media)