[Q] AOSP NeatROM 2.4.1, screen won't turn off topic

I have a Galaxy S2 i9100. I was wondering if it's a known bug that sometimes the screen never turns off unless I press the power button? No matter what I set Display -> Sleep to, the screen often never turns itself off. I can't see any pattern to it for when it works and when it doesn't. Is there any known apps that can mess with it, like NoLED?