I get basically the same error as described in the thread Can't backup iPhone 5s (iOS 8.4) using iTunes 12.3 (because an error occured) or iCloud backup using an iPhone 5 and iOS 9.0.2.
It can neither - backup to iCloud automatically when connected to WiFi and electricity while locked - backup to iCloud manually - backup to iTunes automatically - backup to iTunes manually
I have tried a lot but nothing seems to work so far, and I am hoping to get some input. Here is what I have done so far (unsuccessfully):
- everything in this Apple support article, including rebooting both my MacBook and the iPhone as well as resetting the Lockdown folder
- deleting the old Backup from ~/Library/Application Support/MobileSync/Backup hoping the iTunes backup would be built a-new from scratch
- disabling and re-enabling iCloud backup from my iPhone as well as deleting the old Backup (which incidentally did not seem to work as it is still listed under "last backup" even after deletion)
- the aforementioned thread lead me to search for 'null' or 'zombie' apps (without name) in settings -> general -> memory&iCloud usage – unfortunately, there are none
Any ideas how to fix this?