Custom segue animation – flickering - ios

Question

My custom segue animation works fine, but sometimes I see white-flashes/flickering during the animation. Any tips or suggestions on how to avoid this?
This is my code :
import UIKit
#objc(InsetBlurModalSeque) class InsetBlurModalSeque: UIStoryboardSegue {
override func perform() {
let sourceViewController = self.sourceViewController as UIViewController
let destinationViewController = self.destinationViewController as UIViewController
// Make sure the background is ransparent
destinationViewController.view.backgroundColor = UIColor.clearColor()
// Take screenshot from source VC
UIGraphicsBeginImageContext(sourceViewController.view.bounds.size)
sourceViewController.view.drawViewHierarchyInRect(sourceViewController.view.frame, afterScreenUpdates:true)
var image:UIImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
// Blur screenshot
var blurredImage:UIImage = image.applyBlurWithRadius(5, tintColor: UIColor(white: 1.0, alpha: 0.0), saturationDeltaFactor: 1.3, maskImage: nil)
// Crop screenshot, add to view and send to back
let blurredBackgroundImageView : UIImageView = UIImageView(image:blurredImage)
blurredBackgroundImageView.clipsToBounds = true;
blurredBackgroundImageView.contentMode = UIViewContentMode.Center
let insets:UIEdgeInsets = UIEdgeInsetsMake(20, 20, 20, 20);
blurredBackgroundImageView.frame = UIEdgeInsetsInsetRect(blurredBackgroundImageView.frame, insets)
destinationViewController.view.addSubview(blurredBackgroundImageView)
destinationViewController.view.sendSubviewToBack(blurredBackgroundImageView)
// Add original screenshot behind blurred image
let backgroundImageView : UIImageView = UIImageView(image:image)
destinationViewController.view.addSubview(backgroundImageView)
destinationViewController.view.sendSubviewToBack(backgroundImageView)
// Add the destination view as a subview, temporarily – we need this do to the animation
sourceViewController.view.addSubview(destinationViewController.view)
// Set initial state of animation
destinationViewController.view.transform = CGAffineTransformScale(CGAffineTransformIdentity, 0.1, 0.1);
blurredBackgroundImageView.alpha = 0.0;
backgroundImageView.alpha = 0.0;
// Animate
UIView.animateWithDuration(0.5,
delay: 0.0,
usingSpringWithDamping: 0.6,
initialSpringVelocity: 0.0,
options: UIViewAnimationOptions.CurveLinear,
animations: {
destinationViewController.view.transform = CGAffineTransformIdentity
blurredBackgroundImageView.alpha = 1.0
backgroundImageView.alpha = 1.0;
},
completion: { (fininshed: Bool) -> () in
// Remove from temp super view
destinationViewController.view.removeFromSuperview()
sourceViewController.presentViewController(destinationViewController, animated: false, completion: nil)
}
)
}
}
Thanks.