TreeView AfterExpand event sometimes don't work C#

I have a TreeView and subscribed to the "TreeViewConnections_AfterExpand" and "" event. everyone TreeNode contains MenuScript events. and the following code:

        //event
private void TreeViewConnections_AfterExpand(object sender, TreeViewEventArgs e)
    {
        var activeKey = e.Node.ImageKey.Replace("Inactive", "Active");
        e.Node.ImageKey = activeKey;
        e.Node.SelectedImageKey = activeKey;
    }

//event
private void TreeViewConnections_MouseClick(object sender, MouseEventArgs e)
    {
        var currentNode = this.treeViewConnections.GetNodeAt(e.Location);
        if (currentNode == null) return;
        var currentBounds = currentNode.Bounds;
        Rectangle bounds = new Rectangle(currentBounds.Left - ExpandIcon.Width, currentBounds.Y, currentBounds.Width - 5, currentBounds.Height);
        if (bounds.Contains(e.Location)) return;
        this.treeViewConnections.SelectedNode = currentNode;

        if (e.Button == MouseButtons.Right)
        {
            SetupConnectionMenus(currentNode);
        }
    }

    private void SetupConnectionMenus(TreeNode node)
    {
        var isOpened = node.Nodes.Count > 0;
        if (node.ContextMenu == null)
        {
            var menu = new ContextMenuStrip();
            menu.Items.AddEx("Open Connection", node.Name + "_Open", !isOpened, onClick: OpenConnection_Click, context: node);
            menu.Items.AddEx("Close Connection", node.Name + "_Close", isOpened, onClick: CloseConnection_Click, context: node);
            node.ContextMenuStrip = menu;
        }
    }

   //event
   private void OpenConnection_Click(object sender, EventArgs e)
    {
        var menuItem = sender as ToolStripMenuItem;
        var currentNode = menuItem.Tag as TreeNode;
        OpenConnection(currentNode);
    }

    //event
    private void CloseConnection_Click(object sender, EventArgs e)
    {
        var menuItem = sender as ToolStripMenuItem;
        var currentNode = menuItem.Tag as TreeNode;
        currentNode.Nodes.Clear();
        currentNode.Collapse();
    }

private void OpenConnection(TreeNode node)
    {
        treeViewConnections.BeginUpdate();
        //add child node to  the node.
        treeViewConnections.EndUpdate();
        node.Expand(); //?????
    }

TreeViewConnections_AfterExpand event sometime don't work. as shown in the figure:

But in this case, Is there something else I need to do?