Hi everyone, I just upgraded to iOS 9.2.1 (13D20, the second revision that fix error 53) on my iPhone 6s from the original iOS 9.0 that shipped with the phone, 4 or 5 days ago (can't remember exactly). I thought I had the worst iOS version ever released (iOS 9.0) but I guess I was wrong. Now I'm experiencing some severe battery drains. Let me give some examples. This night, I went to sleep with my phone at 100%, and while I would previously wake up at that same percentage (or worst case at 99%), I woke up with 91%. I was like WTF, what is that so I went checking the battery usage and I noticed that the mail app had 1.5 hours of standby time with only 1 min of active usage. How can that be possible, I open this app like once a day. Also, I noticed that since the upgrade, standby and active usage time are always the same. So if I have 6 hours of usage, I will have 6 hours of standby. This can't be possible, there is clearly something wrong here. Does anyone have/had the same problem as me ? Any tips of how I can fix it before I try the (long) process of backup/restore ?