I have received an error on my backup the last 4 days. This worked correctly for weeks prior to the first error.
The error is as follows: The backup operation that started at '2019-02-25T15:50:49.657335900Z' has failed with following error code '0x8078011E' (Windows Backup failed to get an exclusive lock on the EFI system partition (ESP). This may happen if another application is using files on the ESP. Please retry the operation.). Please review the event details for a solution, and then rerun the backup operation once the issue is resolved.
The error ID is 517
I am not aware of any significant changes from the last day the backup worked to the next day when it did not
File Server is running Server 2016 Standard and backup is being sent to a small NAS.