BoxReorderer Plugin with panels only draggable on header

[Daniil]

Got it.

The BoxReoderer's sources are loaded too late in your scenario.

You can force it to be loaded this way:

protected void Page_Load(object sender, EventArgs e)
{
    if (!X.IsAjaxRequest)
    {
        ResourceManager.RegisterControlResources<BoxReorderer>();
    }
}

[Willimaendu]

You are the best :)! Thank you, that was it!!