Exchange 2013 CU 6 update fails on mailbox role

i am installing cu6 update and everything is fine till i get to the mailbox role service

have no idea why its giving this error

i am installing as the domain administrator

Error:
The following error was generated when "$error.Clear();
          if (($RoleIsDatacenter -ne $true) -and ($RoleIsDatacenterDedicated -ne $true))
          {
            if (test-ExchangeServersWriteAccess -DomainController $RoleDomainController -ErrorAction SilentlyContinue)
            {
              # upgrade the discovery mailboxes to R5 version, this will fix the RecipientDisplayType property of the discovery mailbox which was wrong in R4.
              get-mailbox -RecipientTypeDetails DiscoveryMailbox -DomainController $RoleDomainController | where {$_.IsValid -eq $false} | set-mailbox -DomainController $RoleDomainController
              $name = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxUniqueName;
              $dispname = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxDisplayName;
              $mbxs = @( get-mailbox -Filter {name -eq $name} -IgnoreDefaultScope -resultSize 1 );
              if ( $mbxs.length -eq 0)
              {
                $dbs = @(get-MailboxDatabase -Server:$RoleFqdnOrName -DomainController $RoleDomainController);
                if($dbs.Length -ne 0)
                {
                  $mbxUser = @(get-user -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1);
                  if ($mbxUser.Length -ne 0)
                  {
                    enable-mailbox -Discovery -identity $mbxUser[0] -DisplayName $dispname -database $dbs[0].Identity;
                  }
                }
              }
            }
            else
            {
              write-exchangesetuplog -info "Skipping creating Discovery Search Mailbox because of insufficient permission."
            }  
          }
        " was run: "Microsoft.Exchange.Data.DataValidationException: Database is mandatory on UserMailbox.".

Error:
The following error was generated when "$error.Clear();
          if (($RoleIsDatacenter -ne $true) -and ($RoleIsDatacenterDedicated -ne $true))
          {
            if (test-ExchangeServersWriteAccess -DomainController $RoleDomainController -ErrorAction SilentlyContinue)
            {
              # upgrade the discovery mailboxes to R5 version, this will fix the RecipientDisplayType property of the discovery mailbox which was wrong in R4.
              get-mailbox -RecipientTypeDetails DiscoveryMailbox -DomainController $RoleDomainController | where {$_.IsValid -eq $false} | set-mailbox -DomainController $RoleDomainController
              $name = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxUniqueName;
              $dispname = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxDisplayName;
              $mbxs = @( get-mailbox -Filter {name -eq $name} -IgnoreDefaultScope -resultSize 1 );
              if ( $mbxs.length -eq 0)
              {
                $dbs = @(get-MailboxDatabase -Server:$RoleFqdnOrName -DomainController $RoleDomainController);
                if($dbs.Length -ne 0)
                {
                  $mbxUser = @(get-user -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1);
                  if ($mbxUser.Length -ne 0)
                  {
                    enable-mailbox -Discovery -identity $mbxUser[0] -DisplayName $dispname -database $dbs[0].Identity;
                  }
                }
              }
            }
            else
            {
              write-exchangesetuplog -info "Skipping creating Discovery Search Mailbox because of insufficient permission."
            }  
          }
        " was run: "Microsoft.Exchange.Data.DataValidationException: Database is mandatory on UserMailbox.
   at Microsoft.Exchange.Configuration.Tasks.Task.WriteError(Exception exception, ErrorCategory category, Object target, Boolean reThrow, String helpUrl)
   at Microsoft.Exchange.Configuration.Tasks.Task.WriteError(Exception exception, ErrorCategory category, Object target, Boolean reThrow)
   at Microsoft.Exchange.Configuration.Tasks.DataAccessTask`1.Validate(TDataObject dataObject)
   at Microsoft.Exchange.Configuration.Tasks.SetTaskBase`1.InternalValidate()
   at Microsoft.Exchange.Configuration.Tasks.SetRecipientObjectTask`3.InternalValidate()
   at Microsoft.Exchange.Management.Common.SetMailEnabledRecipientObjectTask`3.InternalValidate()
   at Microsoft.Exchange.Management.RecipientTasks.SetUserBase`2.InternalValidate()
   at Microsoft.Exchange.Management.RecipientTasks.SetMailboxBase`2.InternalValidate()
   at Microsoft.Exchange.Management.RecipientTasks.SetMailbox.InternalValidate()
   at Microsoft.Exchange.Configuration.Tasks.Task.<ProcessRecord>b__b()
   at Microsoft.Exchange.Configuration.Tasks.Task.InvokeRetryableFunc(String funcName, Action func, Boolean terminatePipelineIfFailed)".