The Down Arrow key does not trigger the KeyDown event when the cursor is at position 0 in the TextBox

[Tamilarasan-Paranthaman]

Describe the bug

The KeyDown event is not triggered for the Down Arrow key when the cursor is at position 0 in the TextBox. Only the KeyUp event is fired correctly when pressing the Down Arrow key.

This issue occurs only when the TextBox contains text. If the TextBox is empty, the KeyDown event is triggered as expected.

 <TextBox Height="50"
          Width="200"
          Text="Hello, World!"
          KeyDown="TextBox_KeyDown"
          KeyUp="TextBox_KeyUp">
  </TextBox>

  private void TextBox_KeyDown(object sender, KeyRoutedEventArgs e)
  {
     Debug.WriteLine("The TextBox Key Down fired  : " + e.Key.ToString());
  }

  private void TextBox_KeyUp(object sender, KeyRoutedEventArgs e)
  {
     Debug.WriteLine("The TextBox Key Up fired  : " + e.Key.ToString());
  }

Steps to reproduce the bug

1. Run the attached sample.
2. Tap the TextBox (ensure the cursor is at the 0th position).
3. Press the Down Arrow key on the keyboard.
4. Observe the Output window, the KeyDown event is not triggered, only the KeyUp event is triggered

Sample App

Expected behavior

The KeyDown event should be triggered properly when pressing the Down Arrow key.

Screenshots

TextBox.mp4

NuGet package version

WinUI 3 - Windows App SDK 1.7.1: 1.7.250401001

Windows version

Windows 11 (23H2): Build 22631

Additional context

No response