This is happening because the geometry is marked as "empty", so it doesn't try to render it.

Even if I change the code to check if the Pen has a valid stroke so it tries to render this shape, it fails in some situations where it can't generate any valid stroke cached path
See the following xaml:

  <Grid Width="1000" Height="1000">
    <Rectangle HorizontalAlignment="Stretch" VerticalAlignment="Top" Stroke="Blue" StrokeThickness="30" Margin="100,100,100,0"/>
    <Rectangle HorizontalAlignment="Left" VerticalAlignment="Top" Stroke="Blue" StrokeThickness="30" Margin="100,200,100,0"/>
    <Ellipse HorizontalAlignment="Stretch" VerticalAlignment="Top" Stroke="Blue" StrokeThickness="30" Margin="100,300,100,0"/>
    <Ellipse HorizontalAlignment="Left" VerticalAlignment="Top" Stroke="Blue" StrokeThickness="30" Margin="100,400,100,0"/>
  </Grid>

So, is it because the underlying shape has no area? If there is no good fix, maybe it could be then validated that thickness cannot be larger nor equal than the relevant dimension?

It works fine in Blend, so we should find a way to fix it in our implementation so it renders too.

I understand this is a 3.2.10 issue right?

I was testing just in studio editor v0.1.259-beta. I'm not sure how it matches to the runtime version.

I understand this is a 3.2.10 issue right?

No, it's a problem that it's been there always.

Great, assigned to 3.2.11. I will have a look at this as soon as possible.

Found another instance of a similar problem with lines where Line Thickness matches their width. I attach a sample page reproducing the issue. The workaround for now is using a math converter on the binding fixing the width so we add 1 and they dont match. ( Then it renders )

<Page
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
  mc:Ignorable="d"
  d:DesignWidth="1920"
  d:DesignHeight="1080"
  Background="#FF4D5052" xmlns:noesis="clr-namespace:NoesisGUIExtensions">
  <StackPanel>
    <Line x:Name="PlainLine" X2="100" Stretch="Fill" Stroke="#FF000000" Fill="#FFF4F4F5" StrokeThickness="200" StrokeStartLineCap="Square" StrokeEndLineCap="Round"/>
    <Line x:Name="LineWidthThickness_NotRendering" X2="100" Stretch="Fill" Stroke="#FF000000" Fill="#FFF4F4F5" StrokeThickness="200" StrokeStartLineCap="Square" StrokeEndLineCap="Round" Width="{Binding Path=StrokeThickness, RelativeSource={RelativeSource Self}}" HorizontalAlignment="Left"/>
    <Line x:Name="LineWidthThicknessPlusOne" X2="100" Stretch="Fill" Stroke="#FF000000" Fill="#FFF4F4F5" StrokeThickness="200" StrokeStartLineCap="Square" StrokeEndLineCap="Round" HorizontalAlignment="Left">
      <Line.Width>
        <Binding Path="StrokeThickness" RelativeSource="{RelativeSource Self}">
          <Binding.Converter>
            <noesis:MathConverter Expression="{}{0}+1"/>
          </Binding.Converter>
        </Binding>
      </Line.Width>
    </Line>
  </StackPanel>
</Page>