WPF set Grid column width to max width even if collapsed on SharedSizeGroup

Question

I have a simple Grid with 2 columns and 5 rows. Only 2 of these rows are visible at once. Depending on the selection of a ComboBox in the first row the visibility of the other rows are changed and different UserControls are shown. In the first column is a Label that should describe what to to with the UserControl in the second column (i.e. 'Name', 'Password' and so on). When the Grid is first shown, the second row is Visible and the others are Collapsed. 'Name' just has four letters and for example 'Password' has 8, so the Column.Width changes. So the GUI looks unsteady. What I want is that the Column.Width binds to the maximum (even if momentarily Collapsed) sized Column. We are using language files for different languages here, so I cannot set the size of the first Column to a fixed amount.

This is my code so far:

<Window ...
    ResizeMode="NoResize" SizeToContent="WidthAndHeight">
...
<StackPanel Grid.IsSharedSizeScope="True">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition SharedSizeGroup="LabelColumn" />
            <ColumnDefinition Width="Auto" />
        </Grid.ColumnDefinitions>

        <Label Grid.Column="0" Content="{x:Static base:AppStrings.SecurityMethods}" />
        <ComboBox Grid.Column="1" ItemsSource="{Binding SecurityModes, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" DisplayMemberPath="Value" SelectedValuePath="Key" SelectedValue="{Binding SelectedSecurityMode}" />
    </Grid>

    <Grid Visibility="{Binding SelectedSecurityMode, Converter={StaticResource EqualToVisibilityConverter}, ConverterParameter=Password}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition SharedSizeGroup="LabelColumn" />
            <ColumnDefinition Width="250" />
        </Grid.ColumnDefinitions>
                        
        <Label Grid.Column="0" Content="{x:Static base:AppStrings.Password}" />
        <wpfControls:TextBoxEx Grid.Column="1" Text="{Binding Password}" />
    </Grid>

    <Grid Visibility="{Binding SelectedSecurityMode, Converter={StaticResource EqualToVisibilityConverter}, ConverterParameter=Sms}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition SharedSizeGroup="LabelColumn" />
            <ColumnDefinition Width="250" />
        </Grid.ColumnDefinitions>
                        
        <Label Grid.Column="0" Content="{x:Static base:AppStrings.MobileNumber}" />
        <wpfControls:PhoneNumberControl Grid.Column="1" PhoneNumber="{Binding MobileNumber}" />
    </Grid>

    <Grid Visibility="{Binding SelectedSecurityMode, Converter={StaticResource EqualToVisibilityConverter}, ConverterParameter=Email}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition SharedSizeGroup="LabelColumn" />
            <ColumnDefinition Width="250" />
        </Grid.ColumnDefinitions>

        <Label Grid.Column="0" Style="{StaticResource LabelDefaultStyle}" Content="{x:Static base:AppStrings.EmailAddress}" />
        <wpfControls:TextBoxEx Grid.Column="1" Text="{Binding EmailAddress}" />
    </Grid>

    <Grid Visibility="{Binding SelectedSecurityMode, Converter={StaticResource EqualToVisibilityConverter}, ConverterParameter=None}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition SharedSizeGroup="LabelColumn" />
            <ColumnDefinition Width="250" />
        </Grid.ColumnDefinitions>

        <Label Grid.Column="0" Style="{StaticResource LabelDefaultStyle}" Content="{x:Static base:AppStrings.Password}" IsEnabled="False" />
        <wpfControls:TextBoxEx Grid.Column="1" IsEnabled="False" />
    </Grid>
</StackPanel>

That should be cutted to the essential problem. It later looks like this:

As you can see the first column resized AFTER changing the Visibility. What I want is, that the column takes the space of the maximum sized label without setting all visibilities to Collapsed at a later time. That would also make the GUI look unsteady.