If your iOS device has its display on when you don’t expect it, perhaps you have run into this bug. This iOS 10 bug causes the display to unexpectedly stay on (i.e. not fade to black).
It takes a bit of trial and error to reproduce the bug, but once you get the idea you can cause it to happen once every few tries.
Steps to Reproduce:
1) Click the home or lock button to wake up your iOS device.
2) Wait about 10 seconds until the display just starts to fade then click the home button.
That’s it! If you got the timing right, the display will stay on indefinitely, or until some alert or other action causes it to switch off again. If it fades to black after about 10 seconds again then go back to step one and try again.
This iOS 10 bug has the potential to waste your battery life. For example, if you happen to bump the home button as you are putting your iPhone in your pocket and it was at just the right moment (during the fade out), then you are not likely to notice that the display has stayed on.
This is happening on my iPhone 5, but others have reported it happening on iPhone 5c and it iPhone 6. Comment and let me know if you can reproduce it.
I can confirm that this bug is still occurring in the recently released iOS 10.2.1.