From my observation, iPhone 6 is also affected, and it seems that this bug is occurring quite frequently, and it's not just when trying to close apps with the 3-finger swipe up gesture, switching between apps sometimes causes this bug to occur.
Device May Crash And Respring When Using the VoiceOver Actions Menu to Close the Last Used App Via the App Switcher
If you use the VoiceOver Actions Menu in the App Switcher to close the app that you were just using, you will commonly find that your device will crash and respring. This does not occur if you close other apps.
Bug First Encountered
Device(s) bug has been encountered on
How often the bug occurs