Hi,
Thanks for posting in our forum!
The issue may occur if EFI system partition is locked or other application is using files on the system partition.
I suspect the third party security software protects the system files and causes this issue. Therefore, please
disable security software temporarily and perform clean boot. For about how to perform a clean boot in Windows, please visit:
https://support.microsoft.com/en-us/help/929135/how-to-perform-a-clean-boot-in-windows
If that doesn’t help, uninstall your 3rd party antivirus solution, restart Windows and try
running Windows Server Backup again.
For more information, please refer to the following article.
https://www.winhelponline.com/blog/windows-backup-failed-exclusive-lock-efi-partition-avast/
https://www.kapilarya.com/windows-backup-failed-to-get-an-exclusive-lock-on-the-efi-system-partition-windows-10
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice.
Microsoft does not guarantee the accuracy of this information.
In addition, EFI partition is used for bootloader. Since it is not NTFS dffdormat [it is in FAT32] VSS cannot backup this partition.
Since the data does not change, you can perform on manual backup [not through Win backup] and exclude this from your backup selection.
For more information about this discussion, you can see here:
https://social.technet.microsoft.com/Forums/windowsserver/en-US/6654828e-8cac-4854-b98a-d8f62f15a5ce/windows-backup-failed?forum=windowsbackup
Hope this can help you.
Best Regards,
Daniel
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