System.Exception: An Azure Active Directory call was made (4307766)

When attempting to perform a manual switch the following error is reported in the EmwMIgration.log

Error    System.Exception: An Azure Active Directory call was made to keep object in sync between Azure Active Directory and Exchange Online. However, it failed. Detailed error message:
\tUnable to update the specified properties for on-premises mastered Directory Sync objects or objects currently undergoing migration.
The issue may be transient and please retry a couple of minutes later. If issue persists, please see exception members for more information.

This can be caused by different issues not limited to:

• The TargetAdress is not correct on the target mailbox

• The email address is in conflict with another mailbox in the organization

• The Target address has been changed mid-migration