Affected Version(s):
I have personally seen this error in R9.1, but it may also be in earlier versions.
Problem Details:
When backing up Server Edition configuration, it will reach 20% and then display the following error:
Backup failed: Wait inventory pushed stage failed
Cause:
In my experience, this was caused when trying to backup to the Server Edition itself and there was not enough space on the hard drive to backup to.
Solution:
Increasing hard drive space in the server or pointing the backup to a remote server instead resolved the issue.