The 1407 MAC error is caused by the system not being able to identify a file / folder that is being used on the system.

The reason for this is typically due to the way in which the “finder” application will not be able to identify the various files that you may be trying to manage / change.

To fix this, you need to make sure that the media you're using is absolutely working properly, as well as having any underlying problems at the OS level fixed. To do this, there are several steps through which you should be able to remove any of the files or folders that would be leading the issues to show.

The steps to fix the error include:

  • Transfer any data to external (backup) drive
  • Run OS in “safe boot” mode
  • Try Using Disk Utility
  • Use Command-Line

Ultimately – the error you're seeing is generally the result of using a poor quality USB drive, which is either corrupt or not formatted properly. To ensure the issue does not persist, you need to use the following:

1. Transfer Data To External (Backup) Drive

The first step is to ensure that you are able to move any of the files / folders causing the error to show.

To do this, you'll want to transfer them to a backup drive (preferably an external USB flash drive):

  • Insert a USB drive into an available external USB port
  • Click USB disk icon on desktop
  • Open hard drive causing the error
  • Drag the affected files from the hard drive to the USB
  • Drag USB drive to trash

This should allow you to put the files onto a different disk – basically rewriting the associations inside the system (which should contribute to fixing the error).

2. Run OS In Safe Mode

The next step is to boot up the system in “safe boot” mode.

Like Windows, this allows you to run software and operations without having interference from the likes of drivers or third-party dependencies etc.

You're able to do it as follows:

  • Restart your MAC
  • Press and hold the Shift key after you hear the startup tone
  • Release the Shift key when the Apple logo appears
  • Safe Boot should appear on the Mac OS startup screen

This will allow you to perform hard-drive specific fixes, allowing for the fix of the error itself. The following steps cover this.

3. Run Disk Utility

“Disk Utility” is a tool inside MAC OS which allows its users to fix any undering problems with the hard drive etc.

To ensure this is able to run effectively, you'll want to use the following steps to access & run it:

  • Click on Go> Utilities
  • Double-click “Disk Utility”
  • Select the volume causing errors on the left
  • Click the “First Aid” tab
  • Click “Repair”
  • It should repair the 1407 error

4. Use CLI

The command line utility – just like with Windows – allows you to access applications without having to load them from the GUI.

Whilst it does not do much different to its graphical counterpart, it does get rid of a large number of dependencies which can often cause issues for the OS.

To do this, you can follow the steps below:

  • Whilst in “safe boot” mode, select “Terminal” from Application> Utilities
  • Into the terminal, type “diskutil verify /”
  • Hit Return / Enter and let it scan
  • Restart your system after completion

This should resolve the problem for you.

If there are any further instances of the error, you should consider talking to Apple directly about it.