Hello Virtualmin Support!
We've run across an issue with 'Change Domain Name' -- I think we're blocked in correcting the issue by the fix you put in place for this one:
The issue is that a site owner changed their domain name, which we can't allow in our implementation -- not a big issue there, they changed it back -- but they couldn't change the administration user name back to the original site account owner, because it already exists.
It appears that changing the 'administration user name' does not change anything about the actual administration user account on the system, in our case. Nor does it appear to create a new one, just changes the configuration of the domain in the panel to point to a user that doesn't exist. The site still works, is owned by the administration user and group properly, but Virtualmin backups don't work since it's trying to use credentials for a user which doesn't exist.
There are work-arounds that we've thought about -- such as changing the webmin user manually when the site's admin username is changed, or just updating the mappings in /etc/webmin/virtual-servers/user.dom and /etc/webmin/virtual-servers/domains/<domain UID>, but those didn't seem to be the best first idea in our production environment; didn't want to risk it on experimentation.
I'm not sure I've been very clear -- please let me know if not!