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I'm using iTunes 12.9.5.5 on Mojave (fully updated, to my knowledge). For six months my iPhone 8 (then on iOS 16.5) has not been able to backup to it, neither using USB nor WiFi.

  • Sync seems to work fine otherwise.
  • Older versions of iOS 16 seem to have backed up successfully, judging by last backup date.
  • The error received is my language's equivalent of "...an error occurred while reading from or writing to the iphone".
  • The backup should be smaller than the free space left on the destination volume (~100% margin), judging from the backup size when performed successfully on Windows.

My latest troubleshooting steps have been:

  • Updating to iOS 16.6
  • Trying an older (lower version: 12.6.3.6, older copyright year: 2017) iTunes version on Windows, which successfully performs the backup
  • Try backing up an old iPhone 5 with iOS 10, which works

After these tests I'm left wondering whether this version of iTunes is supposedly capable of performing said backup at all? Can I confirm this somehow? That a lower version on Windows can perform a backup confuses matters somewhat, but the versions might not be directly comparable so I'm left guessing.

Note that this question is specific to macOS Mojave, and as such upgrading to later major releases of macOS is out of scope as a solution.

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  • When you say that it's not backing up via Wi-Fi, do you mean Wi-Fi sync or iCloud. If it's not backing up to iCloud, it would seem to be an issue on the phone. I'm running 11.7 Big Sur and still able to backup, however this is a couple upgrades after your macOS version. Aug 21, 2023 at 13:50
  • @The_Stewart I mean WiFi sync. Although I can initiate a discrete manual backup (over WiFi) without triggering a sync, which also lets me back up to multiple instances of iTunes while still only sync with one of them.
    – Andreas
    Aug 22, 2023 at 12:53

1 Answer 1

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Empirically, yes, using these settings, connected by USB.

enter image description here

Mac Pro 5,1, Mojave, iTunes 12.9.5.5, iPhone SE2020 iOS 16.6. The phone demands trust with a light grey passcode screen before it will start & then sits with a full progress bar [thermometer] for a minute or two before then progressing normally.

I normally only do a local backup manually just before an update, so I hadn't tried since end of July. I don't have auto-sync or sync over wifi on.

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  • Thank you for the confirmation. This will help a lot. The only question right now is whether your version 12.9.9 is a typo or otherwise how I can get hold of it. I did not find such a version listed on Wikipedia.
    – Andreas
    Aug 22, 2023 at 13:05
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    Returning my focus to Mojave I could determine that the only fix was to move the existing device backup out of its current location and do a fresh one. No need for updates. For anyone else with the same problem who doesn't know, you'll find your device's backup in Preferences > Devices. Right-clicking it will let you show it in Finder. Move the folder away and save it until you have finished your new backup.
    – Andreas
    Aug 22, 2023 at 13:33
  • Additional info about the cause of the error message: it gives the erroneous impression that the problem is on the phone side and not the computer side. Turns out there were non-removable directories in the backup directory tree, which in turn pointed to APFS corruption. Unrepairable corruption could then be confirmed in disk utility (both using Mojave and Ventura).
    – Andreas
    Aug 24, 2023 at 17:19
  • "Tunes 12.9.9.5" Do you mean 12.9.5.5? Sep 15, 2023 at 18:10
  • Yup, sorry, typo. Last available for Mojave, sometime 2019 judging by the copyright notice.
    – Tetsujin
    Sep 15, 2023 at 18:12

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