Workaround:
 public class MyRadToggleSwith : RadToggleSwitch
{
    public override string ThemeClassName
    {
        get
        {
            return typeof(RadToggleSwitch).FullName;
         }
    }

    protected override void OnGotFocus(EventArgs e)
    {
        base.OnGotFocus(e);
        this.ToggleSwitchElement.Focus();
     }
}

or simply put focus to the element when the control receives the focus:
private void radToggleSwitch_GotFocus(object sender, EventArgs e)
{
	this.radToggleSwitch1.ToggleSwitchElement.Focus();
}