Listbox scrollbar thumb changes size when content is variable height

Question

I have a ListBox with many objects displayed, each of which can be a variable height, based on the number of values each object has. See my previous question that was answer

Answer 1

Disable virtualization or make the items in your ListBox all of equal height. If you've got less than 100 items or so, you can live without the virtualization.

Answer 2

Set ScrollViewer.CanContentScroll="False" on the ListBox, this will disable what's called "logical scrolling", which does scrolling based on item count instead of height ("physical scrolling").

Answer 3

Why not switch off any size restrictions on the ListBox itself, let it size to contents and wrap it into a ScrollViewer, setting a proper size for the latter?

The markup should look like the following:

    <ScrollViewer Width="640px" Height="480px">
        <ListBox>
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <!--Visualization of a list item-->
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </ScrollViewer>

I saw no thumb size changings during scrolling if it was implemented this way.