VideoPlayback Sample: clean way to start / stop vuforia AR view

So I'm able to reproduce a crash with the 2.8.9 VideoPlayBack Sample and the 2.8.7 SDK which occurs in my project as well. What I want is to be able to jump between 2 View Controllers in a Navigation ViewController Hierarchy: I have a MainViewController which is the rootViewController of the NavigationController and a button tap pushes VideoPlaybackViewController on the navigation Stack. 

Now the crash occurs on iPad3 after 5 times of pushing and popping the VideoPlaybackViewController. 

What I did with the VideoPlayback sample was the following: 

Deleted all SampleAppUI ViewControllers

In AppDelegate: Init MainViewController as navigationcontroller's rootViewController

MainViewController: Has the same startButtonTapped method as SampleAppAboutViewController minus the SampleAppSlidingMenuVC Code:

- (IBAction)startButtonTapped:(id)sender {
    Class vcClass = NSClassFromString(@"VideoPlaybackViewController");
    id vc = [[vcClass alloc]  initWithNibName:nil bundle:nil];
    
    [self.navigationController pushViewController:vc animated:NO];
    [vc release]; // don't leak memory
}

In VideoPlaybackViewController handleDoubleTap: I just pop back to root VC:

// double tap handler
- (void)handleDoubleTap:(UITapGestureRecognizer *)sender {
    [[self navigationController] popToRootViewControllerAnimated:NO];
}

So basically I'm doing all the same like in the sample expect omitting the Sliding Menu VCs. Could anyone tell me what I am missing here?

Thanks in advance