It's kinda a bug with double-tap to wake. It has always been there, sorta. If you put your phone in your pocket with your screen facing your skin, then it detects touches, everywhere, which causes something to crash and you wont be able to unlock it afterwards. This magical bug will appear as long as it detects a lot of different (usually large, like a palm, or ur legs) touches when the screen is off. I've been using DT2W in a lot of ROMs and kernels since kitkat, all of them are the same. Try to put your phone with its screen facing outside when u put it in your pocket.