In case a domain already exists in OA and then it gets transferred from external registrar, DNS hosting resource usage gets incremented, while the actual usage is 0.
At the same time, DNS hosting is changed to "external", breaking name resolution for the domain.
The issue is recognized as POA-100124: Wrong DNS hosting resource usage after external domain transfer.
The issue will be fixed in future product updates.
As a workaround, in order to avoid the problem, increase the DNS hosting resource type limits for the DNS service plans and set them to unlimited.