UiScrollView Adjust Content When Scrolling

Question

I have a problem with my UIScrollView and I hope some of you can help me in some way.

I explain you ...

At the center of my ViewController I have a ScrollView showing the contents of 3 external UIViewController. Through classic for loops I am able to properly display the contents and so far I have not found any problems ...

The problem arises when I perform scrolling between the view controller (horizontally) or, the content of each view controller moves, it does not remain as it was initially set. Now I can not figure out if the problem depends ScrollView or by content, but I think it is a problem of content viewcontroller because I used the autolayout to set constraints ...

At this point I think it's a problem that arises in the ScrollView when I make scrolling to show the next viewcontroller.

Below I insert the screen shoots to show my situation .. as you can see the contents are moved to the right and do not remain in the X position zero.

Can you help me figure out where I'm wrong? what code and 'wrong ..

ScreenShoot

code used

    -(void)initializeViewControllerTour {
    /* Inserisce in una NSMutableArray i ViewController inizializzati da utilizzare*/
    _a_TourVC = [[UPATour alloc] init];
    _a_TourVC = [self.storyboard instantiateViewControllerWithIdentifier:@"A_Tour_App"];

    _b_TourVC = [[UPBTour alloc] init];
    _b_TourVC = [self.storyboard instantiateViewControllerWithIdentifier:@"B_Tour_App"];

    _c_TourVC = [[UPCTour alloc] init];
    _c_TourVC = [self.storyboard instantiateViewControllerWithIdentifier:@"C_Tour_App"];

    _containerArrayVC = [[NSMutableArray alloc] init];
    [_containerArrayVC addObject:_a_TourVC];
    [_containerArrayVC addObject:_b_TourVC];
    [_containerArrayVC addObject:_c_TourVC];

    NSInteger index = 0;

    /* Imposta i valori per la ScrollView */
    CGSize scrollViewSize = CGSizeMake([_containerArrayVC count] * _scrollView.frame.size.width, _scrollView.frame.size.height);

    _scrollView.contentSize = scrollViewSize;
    _scrollView.scrollEnabled = YES;
    _scrollView.showsVerticalScrollIndicator = NO;
    _scrollView.showsHorizontalScrollIndicator = NO;
    _scrollView.pagingEnabled = YES;
    _scrollView.delegate = self;

    /* Imposta il PageControl */
    _pageControl.userInteractionEnabled = NO;
    _pageControl.numberOfPages = [_containerArrayVC count];
    _pageControl.currentPage = index;

    /* Crea il ciclo For per i ViewController basandosi sulla MutableArray */
    for (_currentViewController in _containerArrayVC) {
        [self addChildViewController:_currentViewController];
        CGFloat originx = (index) * _scrollView.frame.size.width;
        _currentViewController.view.frame = CGRectMake(originx, 0, _scrollView.frame.size.width, _scrollView.frame.size.height);
        [_scrollView addSubview:_currentViewController.view];
        [_currentViewController didMoveToParentViewController:self];
        index ++;
    }
}

-(void)scrollViewDidScroll:(UIScrollView *)scrollView {
    CGFloat pageW = _scrollView.frame.size.width;
    CGFloat segmentPage = _scrollView.contentOffset.x / pageW;
    NSInteger page = lround(segmentPage);
    _pageControl.currentPage = page;

}