Content moved after when back to first viewcontroller

Question

I have 2 viewcontrollers in a navigationController.

In the first viewcontroller I have a UIButton that open the second viewcontroller.

When second viewController is load I can see the "back" button on top-left of the screen.

Now, when I come back to the first viewController the content is some points upper than last time.

Like the next image http://imperiosweb.com/tmp/sample.png

Now, first ViewController has a UIScrollView that has the content.

FirstViewController.h

...
@interface FirstViewController : UIViewController{
    IBOutlet UIScrollView *Scroller;
}
@property (weak, nonatomic) IBOutlet UIScrollView *Scroller;
...

FirstViewController.m

...
@implementation FirstViewController
...
@synthesize Scroller  = _scroller;
...

- (void)viewDidLoad
{
  [self.Scroller setBounces:YES];
  ...
}

I don't know if is the center of the scrollView or something else, I was trying to set center, works but doesn't repair the problem (content moved)

- (void)viewDidAppear:(BOOL)animated {

    [self.view setCenter:self.Scroller.center];
    self.Scroller.frame = CGRectMake(0,0,320,416);
    self.Scroller.contentSize = CGSizeMake(320, (550 + self.Scroller.contentOffset.y));
    [self.Scroller setCenter:(CGPointMake(160.0,208.0))];

}

What can I do to fix content like first time (App just launched)?

Thanks!