Hello guidegi,

The mentioned behavior is expected in scenario, when you floating a pane from TabbedMDIControl . After double clicking on the pane, this pane will be docked, but not like a MDIChild, that`s why go into another dockArea. To solve this task, you could handle BeforeToggleDockState() event and include the code below:

private void ultraDockManager1_BeforeToggleDockState(object sender, CancelablePaneEventArgs e)

        {

            if (e.Pane.DockedState == DockedState.Floating && e.Pane.Tag == "IsMdiTabbed")

            {

                e.Cancel = true;

                ((Infragistics.Win.UltraWinDock.DockableControlPane)(e.Pane)).IsMdiChild = true;

            }

            if (e.Pane.DockedState == DockedState.Docked && ((Infragistics.Win.UltraWinDock.DockableControlPane)(e.Pane)).IsMdiChild)

            {

                e.Pane.Tag = "IsMdiTabbed";

            }

            else

            {

                e.Pane.Tag = null;

            }

        }

Please take a  look on attached sample and video file for more details and if you have any questions, feel free to write me

Regards