My family has about a half dozen iPhones and iPads running on iOS9 and they are all experiencing problems with backing up to iCloud. My wife can't back up automatically with phone locked and on WIFI on either her iPad or iPhone. Manual backups seem to work but very slow. My daughter has tried repeatedly to manually back up her iPhone 6 on different wifi systems and she can't do it. Gets a message that the "last backup failed to complete". We have called Applecare about her problem. Neither the technician or supervisor have been able to solve the problem and are escalating the issue. The last backup she was able to do was on October 15. I have encountered several failures to complete the backup on my iPhone 6 when trying it manually and the automatic backups do not work sometimes. My wifi works very well and I usually get 100MBS speed. We are all well below are allotted storage space on iCloud. I have done some searches on this issue and many people have complained about this going back to 2014 so iOS9 can't be blamed entirely. My wife started experiencing problems while on iOS8 and continues to experience it now that she is on iOS9. I am starting to conclude that while the iCloud backup is an excellent idea it is very unreliable.