IPhone : UIVisualEffectView bugs on real iPhone

I have an iPhone application (SceneKit) with a blurView and this is how it is supposed to look like:

When I run it in the simulator it works properly. Then, I ran it on an actual iPhone to see wether it works there too. This was the result:

(I took an external photo because when I took a screenshot it looked as it should)

Now, I realized that when I drag-up the CC it does work again:

I wonder wether this is a bug in the iPhone's firmware (it is on 8.1.2) or wether this results from my code.

Here is the code I use to create the blurEffect:

var blurEffect = UIBlurEffect(style: UIBlurEffectStyle.Dark)
var blurEffectView = UIVisualEffectView()

blurEffectView = UIVisualEffectView(effect: blurEffect)
blurEffectView.frame = CGRectMake(0, 0, screenBounds.size.width, screenBounds.size.height)

self.view.addSubview(blurEffectView)

Do you guys know wether that is my fault or not?