Lag / Delay on ModalViewController dismiss after loading an xib view over SKView - objective-c

Question

Imagine this scenario (some code below):
I have an SKView on a viewcontroller.
I load an xib view (external .xib file) over skview (xib view is a like small menu view that does not cover screen in full).
Then, I show a view controller modally from SKView's controller
When I dismiss this modal view controller, there is a lag on every second dismissal (so, i show it modally, dismiss, it is fine, then i repeat, there is delay, then repeat, works fine, then do again, there is delay ... and so on)
If I do not use SKView (if i just used UIView), that delay does not happen. It only happens when I use SKView.
What may be causing that? Here is simplified code that produces this problem:
#implementation NOZTestController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
// button that loads xib view onto the current skview
UIButton *showxib = [[UIButton alloc] initWithFrame:CGRectMake(20, 80, 280, 30)];
[showxib setTitle:#"Add xib view here" forState:UIControlStateNormal];
[showxib addTarget:self action:#selector(showxibTapped) forControlEvents:UIControlEventTouchUpInside];
// button that loads a view controller programmatically
UIButton *showmodal = [[UIButton alloc] initWithFrame:CGRectMake(20, 120, 280, 30)];
[showmodal setTitle:#"Show modal" forState:UIControlStateNormal];
[showmodal addTarget:self action:#selector(showmodalTapped) forControlEvents:UIControlEventTouchUpInside];
self.view = [[SKView alloc] initWithFrame:self.view.frame];
SKView *v = (SKView *)self.view;
//UIView *v = self.view;
[v addSubview:showxib];
[v addSubview:showmodal];
}
- (void)showxibTapped
{
// displays the xib view
[NOZPlayAgainView presentOnView:self.view inRect:CGRectMake(20, 200, 280, 160) withDelegate:self];
}
- (void)showmodalTapped
{
// displays the modal window
UIViewController *vc = [[UIViewController alloc] init];
UIButton *dismiss = [[UIButton alloc] initWithFrame:CGRectMake(40, 40, 240, 40)];
[dismiss setTitle:#"Dismiss" forState:UIControlStateNormal];
[dismiss addTarget:self action:#selector(dismissModal) forControlEvents:UIControlEventTouchUpInside];
[vc.view addSubview:dismiss];
[self presentViewController:vc animated:YES completion:nil];
}
- (void)dismissModal
{
[self.presentedViewController dismissViewControllerAnimated:YES completion:nil];
}
#end

Answer 1

It is caused by autolayout constraints on the xib view. To arrive to that conclusion, I created a simple view with a subview and added it to SKView. The problem I reported above happened only when I used auto layout constraints to place the subview. I don't know why this is happening but that is the reason for it.