Exchange Server 2013 Cumulative Update 8 Setup fails

I am trying to install CU8 on Exchange 2013 on Server 2012 R2 Std. Set up fails on Mailbox role: Transport Service. Here is the details in the error:

Error:
The following error was generated when "$error.Clear();
          $feVdirName = "PowerShell (Default Web Site)";
          $beVdirName = "PowerShell (Exchange Back End)";
          $vdirName = "PowerShell";
          $InternalPowerShellUrl="http://" + $RoleFqdnOrName + "/powershell";

          get-PowerShellVirtualDirectory -ShowMailboxVirtualDirectories -server $RoleFqdnOrName -DomainController $RoleDomainController | where { $_.Name -eq $beVdirName -or $_.Name -eq $feVdirName } | remove-PowerShellVirtualDirectory -DomainController $RoleDomainController;

          new-PowerShellVirtualDirectory $vdirName -Role Mailbox -DomainController $RoleDomainController -BasicAuthentication:$false -WindowsAuthentication:$true -RequireSSL:$true -WebSiteName "Exchange Back End" -Path ($RoleInstallPath + "ClientAccess\PowerShell-Proxy");
          new-PowerShellVirtualDirectory $vdirName -Role Mailbox -InternalUrl $InternalPowerShellUrl -DomainController $RoleDomainController -BasicAuthentication:$false -WindowsAuthentication:$false -RequireSSL:$false -WebSiteName "Default Web Site" -AppPoolId "MSExchangePowerShellFrontEndAppPool";
        " was run: "System.ArgumentException: The virtual directory 'PowerShell' already exists under 'EXCHANGE.local/Default Web Site'.
Parameter name: VirtualDirectoryName
   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)
   at Microsoft.Exchange.Management.SystemConfigurationTasks.NewExchangeVirtualDirectory`1.InternalValidate()
   at Microsoft.Exchange.Configuration.Tasks.Task.<ProcessRecord>b__b()
   at Microsoft.Exchange.Configuration.Tasks.Task.InvokeRetryableFunc(String funcName, Action func, Boolean terminatePipelineIfFailed)".

I tried rebooting and ran the installer again, but it keeps failing. Thanks!