iPhone backup error - BackupAgent2 - Error uploading "" to "": I have an iPhone 6s and I'm using iOS 11.2.5

I tried running a backup from iTunes, but got the following error:


  iTunes could not back up the iPhone "[iphone name]" because an error occurred while reading from or writing to the iphone.


I've tried multiple computers, OSX, Windows, older iTunes, but always got the same error.

On OSX I've opened the Console app, to see what's going on in the background, and found that the following lines are logged, when the error happens [image]:

error   [date]  BackupAgent2    &lt;private&gt;
error   [date]  BackupAgent2    Error uploading "&lt;private&gt;" to "&lt;private&gt;": &lt;private&gt;
error   [date]  BackupAgent2    Backup error - &lt;private&gt;


I found on some forums that this error log message used to contain a filename instead of &lt;private&gt; (which usually were a corrupted image file) and as a user removed it on the phone, the error disappeared. But it looks like Apple suppressed a lot of things in logs. 

I also found a command sudo log config --mode "private_data:on" to force display these &lt;private&gt; data, but this seems to work on OSX apps only, not on iPhone logs. 

So unfortunately here, I came to a dead end.

Can someone help me identify the corrupted file(s), force displaying more detailed errors, or tell me anything else I can do?
From what you’re describing it looks like you have a corrupted backup on your laptop, I assume deleting it will get you to backup your device. What you can do to check is follow these steps:


In the Finder, navigate to your iTunes backups folder 
The backup folder of your device MUST contain at least the following:


Manifest.db or Manifest.mbdb 
Status.plist 
Manifest.plist 
Info.plist



If you have any of these missing, the backup is corrupted or incomplete. In that case, simply delete this backup and start clean with a new iTunes backup.

I’m also thinking it might be worth checking if any iOS app installed on your iPhone contains files with special characters in the filename -  they can cause issues while backing up (APFS related, yes…). 

I’m sure you’re fine with locating the iTunes backup folder, but just in case anyone else is having trouble here’s how to get there:


Open the Finder
In the Main Menu > Go > Hold alt key, Library menu item appears.
Click Library. 
Navigate to Application Support/MobileSync/Backup and locate the iPhone backup. It should be a folder named with your device UDID.