After a backup has run you may get the following warning:
"Illegal operation attempted on a registry key that has been marked for deletion".
Despite the fact, that it is a warning, the backup is getting not registered. But the backupfile is on the harddrive, and will never be automatically deleted.
Please speak to Support before using the following Registry key, This key will enable the 'Do not forcefully unload the user registry at user logoff' windows policy and probably will solve the issue.
If you set 'DisableForceUnload' registry key, the 'Do not forcefully unload the user registry at user logoff' user policy will be enabled. It means that Windows will not forcefully unload the users registry at logoff, but will unload the registry when all open handles to the per-user registry keys are closed. See this article for details http://blogs.msdn.com/b/dsnotes/archive/2014/03/25/more-on-user-profile-service-functionality.aspx