iPhone screen won't turn off

Hello,

Lately, my iPhone 5S and iPod Touch (both on iOS 7.1.2) screens won't turn off after getting a notification or be manually turned on while on the lock screen. Basically, if I get a notification, the screen would turn on to show the notification on the lock screen. I assume that after a couple seconds the screen would turn off by itself like normal, but instead it stays on until I manually turn it off. When it the problem is occurring, the device overheats and the battery starts to drain. This problem however doesn't occur all the time, but it occurs at random times. When it happens, I turn off the device and it would be fixed temporarily then at random the screen doesn't turn off. I have restored both devices a couple times as a new device every time, and the problem still exists. I also have put the autolock to one minute but still nothing. I am assuming this is a software problem.