When anchored controls are placed into the ExpandablePanel control and panel is collapsed it is possible that Windows Forms layout engine moves the anchored control so it is over the panel header.

To resolve this create ExpandedChanging event handler with following code:

private void expandablePanel1_ExpandedChanging(object sender, 
   DevComponents.DotNetBar.ExpandedChangeEventArgs e)
{
   foreach(Control c in expandablePanel1.Controls)
   {
      if(c!=expandablePanel1.TitlePanel)
      c.Visible = e.NewExpandedValue;
   }
}