I saw this issue too. We actually found a bug in Hasicorp's AzureRM code where they were not setting the source_server_id when importing the replica_server, even though it was being provided correctly from the Azure side. We currently have a ticket open to them to fix the bug, but until their fix, the workaround that we are using is to manually update state in order to set the source_server_id to the primary server correctly, and set the create_mode to "Replica."