Odd WPF Grid Behavior Affected by TextBox Text - wpf

Question

I can't figure out why the contents of my TextBox is affecting my grid column widths. I have setup a grid with 3 columns with widths defined as 50, *, 50, as shown below
Now, when in use, the center column will grow/shrink as the text in the TextBox changes, see the 2 examples below. The actual TextBox is not changing size, so I can't understand why in the world the grid is changing. The Grid is inside of a Border inside a UserControl. The UserControl is used as a DataTemplate in a ListBox.
Edit: I've discovered that this issue is related to the UserControl being in a ListBox, see example image below (UserControl in ListBox (circled in red) vs. UserControl Placed on Form (circed in blue). The grid behaves as expected when the UserControl is placed directly on the form. Code for the form is given below.
UserControl XAML:
<Grid ShowGridLines="True">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="50"/>
<ColumnDefinition Width="1*"/>
<ColumnDefinition Width="50"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<TextBlock Text="Name:" Margin="2" />
<TextBox Grid.Column="1" Margin="2" Text="{Binding Name, UpdateSourceTrigger=PropertyChanged}" Grid.ColumnSpan="2" />
<TextBlock Text="Shift:" Grid.Row="1" Margin="2" />
<TextBox Grid.Column="1" Grid.Row="1" Margin="2" Text="{Binding TimeShift, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, FallbackValue=0}" HorizontalContentAlignment="Right" />
<TextBlock Text="s" Grid.Row="1" Grid.Column="2" Margin="2" />
</Grid>
Window/Form XAML:
<Window x:Class="CrashSimOffice.FileImport"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:CrashSimOffice"
Title="File Import" Height="350" Width="450" Background="White" Icon="/CrashSimOffice;component/Images/16/page-white-save.png">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="75"/>
<ColumnDefinition Width="75"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="75"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Button Content="Add" Margin="2" Command="{Binding AddFileCommand}" />
<Button Content="Remove" Grid.Column="1" Margin="2" Command="{Binding RemoveFileCommand}" />
<ListBox HorizontalContentAlignment="Stretch" Grid.ColumnSpan="4" Margin="2" Grid.Row="1" ItemsSource="{Binding Files}" SelectedItem="{Binding CurrentFile}" ScrollViewer.CanContentScroll="False" Background="WhiteSmoke">
<ListBox.ItemTemplate>
<DataTemplate DataType="{x:Type local:FileViewModel}">
<local:FileView DataContext="{Binding}" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<Button Content="Done" Grid.Column="3" Margin="2" Grid.Row="2" Click="Button_Click" />
<local:FileView Grid.Row="3" Grid.ColumnSpan="4" />
</Grid>

Answer 1

OK, I figured it out, Bruno V you got me thinking it must have something to do with the ListBox. I needed to add this to my ListBox:
ScrollViewer.HorizontalScrollBarVisibility="Disabled"
Not sure why that works, but it does.