Button back ionic disappears

In navigation button often it disappears, maybe it's because I'm redirecting bad, although I think it would be weird because sometimes if it appears and sometimes simply not seen. That confuses the user much of the application and I still can not find solution to this, this happens on both iOS and Android. The way the button position is as follows:

    <ion-nav-bar class="bar-stable">
      <ion-nav-back-button class="button-clear"><i class="icon ion-android-arrow-back"></i></ion-nav-back-button>
    </ion-nav-bar>

$ionicConfigProvider.backButton.previousTitleText(false).text(' ');