UIPageViewController in UINavigationController popping issue - ios

Question

Short story:
Going from UIPageViewController (that presents proper DetailViewController) to UITableViewController, then changing (on didSelectRowAtIndexPath) the DetailViewController of the UIPageViewController and navigationController?.popViewControllerAnimated(true), displays proper UIPageViewController with changed DetailViewController but the whole view is moved down by the height of the navigationBar. Clicking on the screen sends it under the bar (where it should be).
Long story:
I embedded UIPageViewController into UINavigationController. Navigation bar translucent
I created a DetailViewController in my storyboard with a scrollView inside it.
I created custom function in the UIPageViewController to return desired UIViewController
func viewDetailViewController(index: Int) -> DetailViewController? {
if let storyboard = storyboard, page = storyboard.instantiateViewControllerWithIdentifier("DetailViewController") as? DetailViewController {
// Setting the page variables that it stores
return page
}
return nil
}
I set up a code (also in UIPageViewController):
override func viewWillAppear(animated: Bool) {
if let viewController = viewDetailViewController(currentIndex) {
setViewControllers(
[viewController],
direction: .Forward,
animated: false,
completion: nil)
}
}
Then I setup an bar button item to and in the storyboard I connected it to so it perform segue to UITableViewController. I want to pop a viewContorller on cell click so:
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
tableView.deselectRowAtIndexPath(indexPath, animated: true)
self.pageViewController.currentIndex = indexPath.row
navigationController?.popViewControllerAnimated(true)
}
When the view is popped the new view of the UIPageViewController is replaced, the pages work well and everything is great except one thing. The whole view is moved down by the height of the navigationbar. What's even more strange is that (just) tapping on the screen sets the scrollView under the navigationbar (where it should be)
I have also noticed that not only the scrollView is moved down, but what is actually moved down is UIView that contains an UIView that contains the scrollView.
What might be causing this?