Default Nexus screen remains on(over the sleep time)
So the problem is on SOME OCCASION,

the phone doesnt automatically sleep given i set the sleep time to 30 sec, which causes major drainage in my battery life. I use go SMS, and i turned on the msg pop up, it would turn on my screen but wouldnt turn off after the 30 sec. Or let say after i read a email but left it on the table as i assume it will turn off automatically after a given amount of time, it would remain on. So im not sure what's causing it any solution?