iPhone 6 Plus unlocking device screen problem

[Mambain]

Hi guys, I noticed that when I lock my iPhone 6 Plus with some kind of application opened (it's especially noticeable with Whatsapp or Facebook Messenger) and when unlock it again there's an instant apperance of black screen. I mean it only takes like a 0.01s but it's still noticeable and starts to annoy me. It seems like the phone is readjusting resolution or something. I wonder if it's normal or whether it's just my iPhone's problem. My apps are updated and I'm using standard view

 

[maka344]

Restart your device and try again.

 

[Mambain]

Thanks man, it helped!

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Oops, said thanks too early - still happens 🙁