DockSite state incorrect when switching between tabs.

I have a docksite sitting inside of a control inside of a tab with one tool window displayed.   I have an unloaded event handler on the control which saves the state. After either resizing the toolwindow or docking it to another side of the control then clicking on the next tab view, the DockSiteLayoutSerializer.SaveToString does not include my toolwindows position updates.  Then when navigating back, the toolwindows reloads from the serialized file with the incorrect position and dock infomation.