Odd behavior when trying to change a bound RadioButton in WPF

Question

I\'ve bound two radio buttons in my Child window to an Enum in my ViewModel which is constructed in the Main window. The binding works as

Answer 1

EDIT What about converting the enum to bool as follows?

public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
    if (parameter == null || !(bool)value)
        return DependencyProperty.UnsetValue;
    var parameterEnum = parameter as Enum;

    return parameterEnum;
}