At random times, I unlock my iPhone 8 and the springboard is super sluggish with a low framerate, really noticeable when you swipe on the springboard or even open apps. It's dropping frames like crazy. Then I just lock/ unlock it and frame rate gets fixed. Just like that. It seems to be an iOS 11 bug, as I posted this on Reddit and I see multiple users confirming they have same issue, including also on the 8 Plus. I'm hoping this gets fixed asap. Have you had this issue?