Still puzzled if this is a phone issue, an app issue, or just simple the content. Don't suppose you have a song handy that you know there's really good stereo separation in it? I rely on Pink Floyd's 'Money' from their Dark Side of the Moon to test headphones and such. There's very distinct sounds coming from both the left and right channels. Anyway, if you've got a mp3 of a song like that and using a good media player like MX Player or VLC you can determine what is or isn't working properly. If it's hardware that could be more difficult to fix, but if it's just software there's often alternatives. If it's just the content or the service streaming the content, that's going to be an issue.