Steps to reproduce:

1. Create a project
2. Go to Window -> Multiplayer -> Multiplayer Center
3. Verify that the mentioned window opens
4. Doc it above the "Hierarchy", "Scene", and "Game" windows
5. After that, try to move the window next to the "Scene" or "Gave" windows
6. Observe the result

Actual results: "Multiplayer Center" window becomes blank, and "Console" window displays an error. A short video is added below in the "Attachments" window

Expected results: No errors in the Console view.

Reproducible with versions: 1.0.0 (6000.0.48f1, 6000.1.4f1, 6000.2.0b2)

Not reproducible with versions: -

Can’t test with versions: -

Tested on (OS): M1 Max - Sequoia 15.5

Notes: Full error

ArgumentException: Cannot unschedule unknown scheduled function UnityEngine.UIElements.VisualElement+SimpleScheduledItem
UnityEngine.UIElements.TimerEventScheduler.Unschedule (UnityEngine.UIElements.ScheduledItem item) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Scheduler.cs:305)
UnityEngine.UIElements.VisualElement+BaseVisualElementScheduledItem.OnPanelDeactivate () (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/VisualElementScheduler.cs:316)
UnityEngine.UIElements.VisualElement+BaseVisualElementScheduledItem.SendDeactivation () (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/VisualElementScheduler.cs:209)
UnityEngine.UIElements.VisualElement+BaseVisualElementScheduledItem.OnElementDetachFromPanelCallback (UnityEngine.UIElements.DetachFromPanelEvent evt) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/VisualElementScheduler.cs:229)
UnityEngine.UIElements.EventCallbackFunctor`1[TEventType].Invoke (UnityEngine.UIElements.EventBase evt) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/EventCallback.cs:64)
UnityEngine.UIElements.EventCallbackRegistry+DynamicCallbackList.Invoke (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.VisualElement target) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/EventCallbackRegistry.cs:246)
UnityEngine.UIElements.EventDispatchUtilities.HandleEventAtTargetAndDefaultPhase (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.VisualElement target) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/EventDispatchUtilities.cs:116)
UnityEngine.UIElements.VisualElement.WillChangePanel (UnityEngine.UIElements.BaseVisualElementPanel destinationPanel) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/VisualElement.cs:1955)
UnityEngine.UIElements.VisualElement.SetPanel (UnityEngine.UIElements.BaseVisualElementPanel p) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/VisualElement.cs:1881)
UnityEngine.UIElements.VisualElement+Hierarchy.SetParent (UnityEngine.UIElements.VisualElement value) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/VisualElementHierarchy.cs:855)
UnityEngine.UIElements.VisualElement+Hierarchy.RemoveAt (System.Int32 index) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/VisualElementHierarchy.cs:648)
UnityEngine.UIElements.VisualElement+Hierarchy.Remove (UnityEngine.UIElements.VisualElement child) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/VisualElementHierarchy.cs:607)
UnityEngine.UIElements.VisualElement.RemoveFromHierarchy () (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/VisualElementHierarchy.cs:967)
UnityEditor.UIElements.DefaultEditorWindowBackend.RemoveRootElement (UnityEngine.UIElements.VisualElement root) (at /Users/bokken/build/output/unity/unity/Modules/UIElementsEditor/WindowBackends/DefaultEditorWindowBackend.cs:177)
UnityEditor.UIElements.DefaultEditorWindowBackend.UnregisterWindow () (at /Users/bokken/build/output/unity/unity/Modules/UIElementsEditor/WindowBackends/DefaultEditorWindowBackend.cs:154)
UnityEditor.UIElements.DefaultEditorWindowBackend.UnityEditor.IEditorWindowBackend.OnUnregisterWindow () (at /Users/bokken/build/output/unity/unity/Modules/UIElementsEditor/WindowBackends/DefaultEditorWindowBackend.cs:109)
UnityEditor.HostView.DeregisterSelectedPane (System.Boolean clearActualView, System.Boolean sendEvents, System.Boolean isSwitchingTab) (at /Users/bokken/build/output/unity/unity/Editor/Mono/HostView.cs:669)
UnityEditor.DockArea.RemoveTab (UnityEditor.EditorWindow pane, System.Boolean killIfEmpty, System.Boolean sendEvents) (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/DockArea.cs:220)
UnityEditor.DockArea.PerformDrop (UnityEditor.EditorWindow w, UnityEditor.DropInfo info, UnityEngine.Vector2 screenPos) (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/DockArea.cs:333)
UnityEditor.DockArea.DragTab (UnityEngine.Rect tabAreaRect, System.Single scrollOffset, UnityEngine.GUIStyle tabStyle, UnityEngine.GUIStyle firstTabStyle) (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/DockArea.cs:1091)
UnityEditor.DockArea.DrawTabs (UnityEngine.Rect tabAreaRect) (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/DockArea.cs:431)
UnityEditor.DockArea.OldOnGUI () (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/DockArea.cs:399)
UnityEngine.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 parentTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout, UnityEngine.Rect layoutSize, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/IMGUIContainer.cs:432)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/IMGUIContainer.cs:723)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/IMGUIContainer.cs:693)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Boolean canAffectFocus) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/IMGUIContainer.cs:686)
UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUIRaw (UnityEngine.UIElements.EventBase evt, System.Boolean canAffectFocus, System.Boolean verifyBounds) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/IMGUIContainer.cs:646)
UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUI (UnityEngine.UIElements.EventBase evt, System.Boolean canAffectFocus, System.Boolean verifyBounds) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/IMGUIContainer.cs:635)
UnityEngine.UIElements.IMGUIContainer.HandleEventBubbleUp (UnityEngine.UIElements.EventBase evt) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/IMGUIContainer.cs:787)
UnityEngine.UIElements.EventDispatchUtilities.HandleEventAcrossPropagationPathWithCompatibilityEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.EventBase compatibilityEvt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.VisualElement target, System.Boolean isCapturingTarget) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/EventDispatchUtilities.cs:304)
UnityEngine.UIElements.EventDispatchUtilities.DispatchToCapturingElementOrElementUnderPointer (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, System.Int32 pointerId, UnityEngine.Vector2 position) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/EventDispatchUtilities.cs:545)
UnityEngine.UIElements.PointerUpEvent.Dispatch (UnityEngine.UIElements.BaseVisualElementPanel panel) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/PointerEvents.cs:1642)
UnityEngine.UIElements.EventDispatcher.ProcessEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/EventDispatcher.cs:419)
UnityEngine.UIElements.EventDispatcher.Dispatch (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.DispatchMode dispatchMode) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/EventDispatcher.cs:215)
UnityEngine.UIElements.BaseVisualElementPanel.SendEvent (UnityEngine.UIElements.EventBase e, UnityEngine.UIElements.DispatchMode dispatchMode) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Panel.cs:641)
UnityEngine.UIElements.UIElementsUtility.DoDispatch (UnityEngine.UIElements.BaseVisualElementPanel panel) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/UIElementsUtility.cs:543)
UnityEngine.UIElements.UIElementsUtility.UnityEngine.UIElements.IUIElementsUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& eventHandled) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/UIElementsUtility.cs:243)
UnityEngine.UIElements.UIEventRegistration.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/UIElementsUtility.cs:78)
UnityEngine.UIElements.UIEventRegistration+<>c.<.cctor>b__1_2 (System.Int32 i, System.IntPtr ptr) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/UIElementsUtility.cs:32)
UnityEngine.GUIUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& result) (at /Users/bokken/build/output/unity/unity/Modules/IMGUI/GUIUtility.cs:224)