When allowing DocumentWindows to float (CanDocumentWindowsRaft = true), a DocumentWindow will float fine when dragging it outside the TabbedMdiContainer. However, when docking the window back into the TabbedMdiContainer via dragging, there's an empty window still floating in the DocumentWindow's last location. Other methods of docking (Dock option, double-clicking the title bar) seem to work as expected.
While I first discovered this in my application, it can be reproduced in the sample browser.
1. Go to the Docking & MDI category and select Features (both external and in-line will work)
2. Drag one of the DocumentWindow tabs (eg WelcomeDocument.rtf or ReadOnlyDocument.txt) outside the TabbedMdiContainer so it floats
3. Drag the DocumentWindow back into the TabbedMdiContainer to dock it (doesn't matter if it's docked to the side or re-added as a tab)
The DocumentWindow should now be docked, with a blank window still floating.