Back button inside UISplitViewController disappears after rotate

Question

i have an iOS app structured more or less like this:

UISplitViewController
-> (Master View) UITableViewController
-> (Detail View) UITabBarController
   -> Tab 1
      -> UINavigationController
         -> ViewController 1, ViewController 2

When I'm in "ViewController 2" I have the back button, in the navigation bar, for return to "ViewController 1" BUT, when i rotate the iPad (for example from portrait to landscape) the "Back" button disappears, and it never reappear back.

What could be the cause? I'm using xCode 8.2 and the iPad have iOS 8.1.

SOME OTHER DETAILS:

1. The Button is always hidden when I start the app from landscape.
2. The Storyboard is instantiated manually in AppDelegate.