Commented Unassigned: Exception when editing a Task [12239]

I'm getting this when editing a Task and trying to change the behaviour if the Task is already running.

System.InvalidCastException was unhandled
HResult=-2147467262
Message=Specified cast is not valid.
Source=Microsoft.Win32.TaskSchedulerEditor
StackTrace:
at Microsoft.Win32.TaskScheduler.TaskPropertiesControl.taskMultInstCombo_SelectedIndexChanged(Object sender, EventArgs e)
at System.Windows.Forms.ComboBox.OnSelectedIndexChanged(EventArgs e)
at System.Windows.Forms.ComboBox.WmReflectCommand(Message& m)
at System.Windows.Forms.ComboBox.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
InnerException:

I'm calling the UI Dialog as follows:

Microsoft.Win32.TaskScheduler.Task dct = null;

try
{
dct = util.CreateTask();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}

if (dct != null)
{
TaskEditDialog ted = new TaskEditDialog(dct, true, true);
try { ted.ShowDialog(); }
catch (Exception ex) { MessageBox.Show(ex.Message); }
}

Windows 10 Professional. Visual Studio 2012. Nuget packages installed Sep 2015. Any assistance gratefully received.
Comments: ** Comment from web user: DonAtVega **

The exception is thrown in the "ted.ShowDialog();" call. It only occurs if you try to change the "If the task is currently running then the following rule applies" combo-box control.

I've tested it on Windows Server 2012 R2 and it breaks on that as well...even when you "Run As Administrator" (if you don't "Run As Administrator" then my exception handling steps in.