Hello
We recently upgraded a project from Ext.Net 2.3 to 4.4. We have a lot of dropdown with a treepanel as their components. These are not working correctly now, when expanding nodes the drop-down collapses and user needs to expand the dropdown again to navigate the tree.
I could reproduce this in examples project, based on treepanel with loader (.ashx).
<%@ Page Language="C#" %>

<!DOCTYPE html>

<html>
<head runat="server">
    <title>TreePanel with ajax proxy using HttpHandler - Ext.NET Examples</title>
    <link href="/resources/css/examples.css" rel="stylesheet" />
</head>
<body>
    <form runat="server">
        <ext:ResourceManager runat="server" />

        <h1>TreePanel with ajax proxy using HttpHandler</h1>
        <ext:DropDownField runat="server" Width="500">
            <Component>
        <ext:TreePanel
            ID="TreePanel1" RootVisible="False"
            runat="server"
            Title="Tree"
            Height="300"
                    Width="200"
                    Shadow="false"
                    UseArrows="true"
                    AutoScroll="true"
                    ContainerScroll="true"
                    >
            <Store>
                <ext:TreeStore runat="server">
                    <Proxy>
                        <ext:AjaxProxy Url="TreeLoader.ashx" />
                    </Proxy>
                </ext:TreeStore>
            </Store>
            <Root>
                <ext:Node NodeID="0" Text="Root" />
            </Root>
        </ext:TreePanel>        
            </Component>
        </ext:DropDownField>
        
    </form>
</body>
</html>
To Reproduce
Click Dropdown to expand, now expand some nodes and then their children, you will see the 'picker' element gets closed. This is annoying for the user.