Back button title impossible to change

Hello guys,

First of all thanks for your work.

I have one problem:
1) I perform a Segue from leftviewcontroller
2) I active the navigation bar and back button in the new ViewController
3) But I don't know why it´s impossible for me to change the backbutton title, always have "back" title

In you example it's something like go to the subContentView from leftSlideMenu.
But I don't have the SlideMenu declared on app delegate so I have:

ContainerVC
-> LeftVC
-> RightVC
-> MainNavigationController -> MainVC -> A

So i wanna go from LeftVC to A ...