To reproduce:
public Form1()
{
    InitializeComponent();

    this.radPanorama1.ShowGroups = true;
    TileGroupElement group = new TileGroupElement();
    group.Name = "Group1";
    this.radPanorama1.Groups.Add(group);
    for (int i = 0; i < 20; i++)
    {
        group.Items.Add(new RadTileElement());
    }
    group.RowsCount = 5;

    this.radPanorama1.ScrollBarAlignment = HorizontalScrollAlignment.Bottom;
}

Workaround: set the ScrollBarAlignment property to HorizontalScrollAlignment.Top