A Reddit user uncovered a very-hard-to-reproduce bug in iOS 10.3.1 that could cause an iPhone to freeze up for a few seconds and then respring. It takes a lot of tries, and basically seems only possible to do when you're actually trying to do so, but it exists, and can be reproduced, so I'm letting you know about it.
Don't worry, it's not a major issue, and you probably won't ever trigger this bug unless you do it on purpose.
When you tap three fingers on three different sections in Control Center simultaneously, it might cause your iPhone to freeze up.
The freeze happens under different circumstances. I pressed AirDrop, Night Shift, and the Camera on my iPhone 7 Plus to produce the bug, but had to press AirPlay, Night Shift, and the Camera on my iPhone SE. Others have reported that it happens when pressing AirPlay, Night Shift, and the Calculator or AirPlay, Night Shift, and the Timer.
It freezes for just a few seconds, and then resprings — or reloads the system. It doesn't shut down or restart. When it reloads, you don't even have to enter your Passcode to unlock your iPhone. You can use Touch ID, which is a clear sign that the system didn't shut down or restart.
If you decide to try to reproduce the bug and your iPhone freezes, but doesn't respring, make sure you know how to fix a frozen iPhone
It appears to affect all models of iPhone 5s and newer. I was able to reproduce the bug on my iPhone 7 Plus and my iPhone SE. Some Reddit posters noted that it happened on iPhone 6, iPhone 6s, and iPhone 7. One commenter said he was able to reproduce the bug on an iPhone SE running iOS 10.2.
We filed a Radar with Apple . It's possible that it's already been fixed with the latest iOS 10.3.2 beta, but Apple might not have even known of its existence before today. They know now, and will likely fix it in an update soon.