What controls the motion gesture to wake up the lockscreen?

I searched through the forum and really couldnt find what I was looking for, so apologies if its there and I missed it.

Can anyone point me to what controls the double tap to wake gesture? It has always worked for me, even without using sense but after updating to 5.0.1 and loading up Nova and Next (used C locker previously) the double tap to unlock doesnt work. After it stopped working I think it has worked a handful of times in the interim. I have tried re-enabling some things, but cant seem to find what I did that is causing it to be disabled so any guidance in the right direction is appreciated.

Thanks