onMarkerComplete has been broken since 2014.

[Tilde]

game.bgm = game.add.audio('southSide');
game.bgm.addMarker('start', 0, 11.748, 0.7);
game.bgm.addMarker('loop', 11.748, 110.769, 0.7, true);
game.bgm.play('start', 0, 0.7, false);
game.bgm.onMarkerComplete.add(function() { // This will only fire once, and the sound will NOT loop after heading into the loop section under any circumstances
      if (game.bgm.volume != 0.0) {
           console.log('yes');
           game.bgm.play('loop', 0, 0.7, true);
     }
}, this);

I did a search on this and it turns out it's just never been fixed!

[rich]

If there has never been a GitHub issue created for it, then it would never have been known about to fix it (hint hint)

[Tilde]

I'll probably do that from now on instead of my current strategy of commenting "god damn it, Rich" everywhere I use audio

[rich]

Put it this way: no issue, no fix.