Unhappy [Q] [4.4.2] Screen does not turn off after a reboot! Not with power button either

This is the single most frustrating bug I have ever encountered, within a month on two different phones. I was using a Galaxy SII running Kitkat ROMs and this bug occurred on each ROM - and I've just bought a Lenovo S860 which was officially updated to kitkat yesterday and now this same darn thing just happened again!

The bug: After a normal day or two's usage a simple reboot results in the screen/display staying on permanently. It does not respond to the Power button at all - although the power button works perfectly if I need to reboot or power off the phone.

Each time the only solution I can think of is to factory reset which is so frustrating. I don't know why this bug has happened to me on two different devices now; the common features I can think of are that on each phone I had Developer options enabled (but 'keep screen on during charging' unchecked) - I use Dynamic Notifications as a primary lockscreen. I keep display timeout at 1 minute. Other than that I use a few very standard News/Productivity apps none of which have anything to do with keeping the display on and rendering the power button useless.

Lenovo S860 that I'm currently on is not rooted and is full stock so I haven't tinkered around with the system at all either.

I would appreciate any help, any hint or guidance or just plain anything. I'm literally afraid to reboot my phone now, I can't keep setting up the phone after a reset every two or three days.