Exchange 2013 CU10 - Update from CU3 - Exchange_Online-ApplicationAccount@domain.local" of property "UserPrincipalName" is used by another recipient object. Please specify a unique value.

When attempting to updated Exchange 2013 from CU3 to CU10, I am getting an error during stage 1 (Organisation Preparation).

Full log can be seen below...

Error:

The following error was generated when "$error.Clear();

            #

            # O15# 2844081 - Create PartnerApplication "Exchange Online" in DC and On-Premise

            #

            $exch = [Microsoft.Exchange.Data.Directory.SystemConfiguration.WellknownPartnerApplicationIdentifiers]::Exchange;

            $exchApp = Get-PartnerApplication $exch -ErrorAction SilentlyContinue -DomainController $RoleDomainController | Where { $_.UseAuthServer };

            if ($exchApp -eq $null)

            {

                $exchAppName = "Exchange Online";

                $exchApp = New-PartnerApplication -Name $exchAppName -ApplicationIdentifier $exch -Enabled $RoleIsDatacenter -AcceptSecurityIdentifierInformation $false -DomainController $RoleDomainController;

            }

            # Create application account for Exchange

            $appAccountName = $exchApp.Name + "-ApplicationAccount";

            $appAccount = Get-LinkedUser -Identity $appAccountName -ErrorAction SilentlyContinue -DomainController $RoleDomainController;

            if ($appAccount -eq $null)

            {

                $appAccountUpn = $appAccountName.Replace(" ", "_") + "@"+ $RoleFullyQualifiedDomainName;

                $appAccount = New-LinkedUser -Name $appAccountName -UserPrincipalName $appAccountUpn -DomainController $RoleDomainController;

                Set-PartnerApplication -Identity $exchApp.Identity -LinkedAccount $appAccount.Identity -DomainController $RoleDomainController;

            }

            foreach ($roleName in ("UserApplication", "ArchiveApplication", "LegalHoldApplication","Mailbox Search", "TeamMailboxLifecycleApplication", "MailboxSearchApplication"))

            {

                $roleIdentity = Get-ManagementRole $roleName -DomainController $RoleDomainController;

                $roleAssignment = Get-ManagementRoleAssignment -Role $roleIdentity.Identity -RoleAssignee $appAccount.Identity -DomainController $RoleDomainController;

                if ($roleAssignment -eq $null)

                {

                    New-ManagementRoleAssignment -Role $roleName -User $appAccount.Identity -DomainController $RoleDomainController;

                }

            }

        " was run: "Microsoft.Exchange.Configuration.ObjectModel.PropertyValueExistsException: The value "Exchange_Online-ApplicationAccount@domain.local" of property "UserPrincipalName" is used by another recipient object. Please specify a unique value.

   at Microsoft.Exchange.Configuration.Tasks.Task.ThrowError(Exception exception, ErrorCategory errorCategory, Object target, String helpUrl)

   at Microsoft.Exchange.Configuration.Tasks.Task.WriteError(Exception exception, ErrorCategory category, Object target, Boolean reThrow)

   at Microsoft.Exchange.Configuration.Tasks.Task.WriteError(LocalizedException exception, ExchangeErrorCategory category, Object target)

   at Microsoft.Exchange.Configuration.Tasks.RecipientTaskHelper.IsPropertyValueUnique(IRecipientSession recipientSession, ADScope scope, ADObjectId selfId, ADPropertyDefinition[] propertyDefinitionsToSearch, ADPropertyDefinition propertyDefinitionToReportError, Object value, Boolean showDuplicatedObjectInError, TaskVerboseLoggingDelegate logHandler, ErrorLoggerDelegate errorHandler, ExchangeErrorCategory errorLoggerCategory, Boolean includeSoftDeletedObjects)

   at Microsoft.Exchange.Configuration.Tasks.RecipientTaskHelper.IsUserPrincipalNameUnique(IRecipientSession recipientSession, ADRecipient recipient, String userPrincipalName, TaskVerboseLoggingDelegate logHandler, ErrorLoggerDelegate writeError, ExchangeErrorCategory errorLoggerCategory, Boolean excludeSelfCheck)

   at Microsoft.Exchange.Configuration.Tasks.RecipientTaskHelper.IsUserPrincipalNameUnique(IRecipientSession recipientSession, ADRecipient recipient, String userPrincipalName, TaskVerboseLoggingDelegate logHandler, ErrorLoggerDelegate writeError, ExchangeErrorCategory errorLoggerCategory)

   at Microsoft.Exchange.Management.RecipientTasks.NewLinkedUser.PrepareRecipientObject(ADUser user)

   at Microsoft.Exchange.Configuration.Tasks.NewRecipientObjectTaskBase`1.PrepareDataObject()

   at Microsoft.Exchange.Configuration.Tasks.SetTaskBase`1.InternalValidate()

   at Microsoft.Exchange.Management.RecipientTasks.NewLinkedUser.InternalValidate()

   at Microsoft.Exchange.Configuration.Tasks.Task.<ProcessRecord>b__b()

   at Microsoft.Exchange.Configuration.Tasks.Task.InvokeRetryableFunc(String funcName, Action func, Boolean terminatePipelineIfFailed)".

Does anyone have any steps to overcome this?