Hi Norman, unfortunately the screen that runs does not generate a logfile with the details.

If you get the message "Backup failed" after the backup process ran for a while, indicates one or more files are in use or inaccessible to include in the backup.

Please see the following article for more details:

• Error: 'Backup Failed' when you are making a backup

Suggestion: If the backup file created, you can also compare the folder contents with the backup file, as the file in use will be missing from the created backup. 

We hope that this will help you to resolve the issue.