Symptoms
You may see DNS records being added with the domain appearing twice. For example, when adding the subdomain subdomain.example.com, the record is added as subdomain.example.com.example.com.
Description
This can occur if a full domain or subdomain is provided but it does not end with a "." (period) character. The domain will be appended to any name entry that does not end in a "." character.
Workaround
When adding a record, either the full name should be provided with a "." at the end, or only the portion proceeding the domain should be used. For example, the following would be valid ways to add a subdomain record.
subdomain
subdomain.example.com.