These are the steps to reproduce the bug:

1. Start dragging a docked window tab (but don't leave the tab bounds for now).
2. While still holding the left mouse button, click the right mouse button to let the context menu appear.
3. Now drag the tab outside the tab bar until the window gets undocked (for example to the blue region above the docked windows).
4. Finish dragging by releasing the left mouse button.
5. Move the mouse cursor over the title bar of another docked window -> the window is undocked without interacting with it and will stick to the cursor until you click the mouse button to release it.

Workaround:
   bool flag = false;
        public Form1()
        {
            InitializeComponent();
            
            ContextMenuService menuService = this.radDock1.GetService<ContextMenuService>();
            menuService.ContextMenuDisplaying += menuService_ContextMenuDisplaying;

            DragDropService service = this.radDock1.GetService<DragDropService>();
            service.Starting += service_Starting;
        }

        void service_Starting(object sender, StateServiceStartingEventArgs e)
        {
            e.Cancel = flag;
            flag = false;
        }

        void menuService_ContextMenuDisplaying(object sender, ContextMenuDisplayingEventArgs e)
        {
            flag = true;
        }