I run a number of sub-sites from my main multi-site at cloudbestpractices.net
I wanted to add some more sites, which had domains associated with previously dedicated installations, to consolidate them all under the one multi-site.
I couldn't get the domain mapping to work although the DNS was set up the same as the working sites, so it was suggested this could be because the domains were still on my hosting accounts as add-ons, which they were.
I have just removed them, and for some reason this has broken all my other sub-site domain mappings. For example DigitalGovernment.io and CanadaCloud.net. The Wordpress sites are all fine, it's just the domain pointing that's broken, the domain mapping tool now says they are invalid.
The domain I had wanted to move and had just deleted is ScotVote.info.