Why does the event "MouseLeftButtonUp" not work or get triggered most of the time?

Question

For simplifying the problem, I created a simple code snippet with the same problem:

<Window x:Class="WPFTest.MainWindow"
        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"
        xmlns:local="clr-namespace:WPFTest"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Canvas x:Name="drawingCanvas" 
            MouseLeftButtonDown="drawingCanvas_MouseLeftButtonDown" 
            Background="White" 
            MouseMove="drawingCanvas_MouseMove" 
            MouseLeftButtonUp="drawingCanvas_MouseLeftButtonUp" />
    </Grid>
</Window>

When I try to use the MouseLeftButtonUp event, it does not work most of the time. Also by using PreviewMouseLeftButtonUp. Can someone tell me why it is like this and offer any suggestions to solve this problem?

namespace WPFTest
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            drawMode = false;
            startPoint = new Point();
            endPoint = new Point();
        }

        private bool drawMode;
        private bool alreadyForm;
        private Point startPoint;
        private Point endPoint;
        
        private void drawingCanvas_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            drawMode = true;
            alreadyForm = false;
            startPoint = e.GetPosition(drawingCanvas);
        }

        private void drawingCanvas_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            drawMode = false;
            alreadyForm = false;
            Debug.WriteLine("the event was detected.");
        }

        private void drawingCanvas_MouseMove(object sender, MouseEventArgs e)
        {
            if (drawMode)
            {
                if (alreadyForm) 
                     drawingCanvas.Children.RemoveAt(drawingCanvas.Children.Count-1);

                endPoint = e.GetPosition(drawingCanvas);

                Line newLine = new Line();
                newLine.X1 = startPoint.X;
                newLine.Y1 = startPoint.Y;
                newLine.X2 = endPoint.X;
                newLine.Y2 = endPoint.Y;

                newLine.Stroke = Brushes.Black;
                newLine.StrokeThickness = 4;

                drawingCanvas.Children.Add(newLine);

                alreadyForm = true;
            }
        }
    }
}

I tried to solve the problem with the PreviewMouseLeftButtonUp event but it was the same.

I tried to use e.Handled = true; but it's also the same