GPS is quitting its function when screen is off. This is mostly noticable when using a sportsapp like Endomondo (or Runkeeper or other apps that use GPS). When GPS signal is found, the app registers the location just fine. But after about 3.5 ~ 4 minutes (screen off) the device stops recording location. This happens 100 percent of the times. When the screen is turned on again, the GPS signal is quickly found again and the device will start recording location again. Most likely this has something to do with switching to a low powerstate when the screen is off. Earlier versions (I think < 6 ) did not have this problem. All 6.x.x versions do have it.