❔ WPF Converter Infinite call

<UserControl.Resources>
    <converters:RelativeFontSizeConverter
        x:Key="RelativeFontSizeConverter"
        WhenInvalid="15" />
    <converters:MathConverter x:Key="MathConverter" />
</UserControl.Resources>
<Grid Margin="14,14">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="auto" />
        </Grid.ColumnDefinitions>

        <Grid Grid.Column="0">
            <Grid.RowDefinitions>
                <RowDefinition Height="3*" />
                <RowDefinition Height="2*" />
            </Grid.RowDefinitions>

            <TextBlock
                Grid.Row="0"
                d:Text="Tell Mark"
                FontSize="{Binding ActualHeight, ConverterParameter='0.7', Converter={StaticResource RelativeFontSizeConverter}, RelativeSource={RelativeSource Self}}"
                FontWeight="SemiBold"
                Foreground="{StaticResource BrushFgDefault}"
                Text="{Binding Todo.Title}"
                TextTrimming="CharacterEllipsis" />

            <TextBlock
                Grid.Row="1"
                d:Text="Tell Mark the details of the project that he has been recently included in"
                FontSize="{Binding ActualHeight, ConverterParameter='0.7', Converter={StaticResource RelativeFontSizeConverter}, RelativeSource={RelativeSource Self}}"
                Foreground="{StaticResource BrushFgMuted}"
                Text="{Binding Todo.Description}"
                TextWrapping="Wrap" />
        </Grid>


        <!--  scalable square button up to 80x80  -->
        <Viewbox
            Grid.Column="1"
            MaxWidth="80"
            MaxHeight="80"
            VerticalAlignment="Top"
            Stretch="Uniform">
                    ...
        </Viewbox>
    </Grid>
</Grid>