Ever since I have updated to 8.1, my retina iPad mini is having trouble entering standby mode. I originally thought it was an issue with Alien Blue but it has started happening with other apps such as Notability. When I go to battery > usage, the usage and standby time are always the same even though the screen was off and smart cover on. This usually leads to a 30-40% battery drain overnight. Is there anyway to fix this? Background app refresh is off.