Commenced a full O365 migration without success

On one of my sites, I commenced a full O365 migration. SO far, many of the mailboxes were moved successfully and without any issues. Trouble started with one batch, where I got Azure AD failure when migration was complete (or incomplete if you will). This is the error message I am getting right now:

“Warning: The following failure occurred after the Active Directory modification completed: The domain controller ‘SN1PR16A001DC06.NAMPR16A001.PROD.OUTLOOK.COM’ is not available for use at the moment. Please try again.”

What might be the cause for this, especially if other batches were ok?

Please follow the below link