1) Add the attached script Bug.cs to a new project

2) Open the UI Builder and add the MonoBehaviourBinding element to the canvas.

3) Select the element. Note the errors in the console.

 
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NullReferenceException: Object reference not set to an instance of an object
Unity.UI.Builder.BuilderDataSourceAndPathView.UpdateAttribute (UnityEngine.UIElements.VisualElement target, System.String bindingAttribute) (at C:/Unity/Source/unity-worktree1/Modules/UIBuilder/Editor/Builder/Inspector/Binding/BuilderDataSourceAndPathView.cs:185)
Unity.UI.Builder.BuilderDataSourceAndPathView+<>c__DisplayClass47_0.<OnPropertyFieldBound>b__0 () (at C:/Unity/Source/unity-worktree1/Modules/UIBuilder/Editor/Builder/Inspector/Binding/BuilderDataSourceAndPathView.cs:153)
UnityEngine.UIElements.VisualElement+SimpleScheduledItem.PerformTimerUpdate (UnityEngine.UIElements.TimerState state) (at C:/Unity/Source/unity-worktree1/Modules/UIElements/Core/VisualElementScheduler.cs:321)
UnityEngine.UIElements.TimerEventScheduler.UpdateScheduledEvents () (at C:/Unity/Source/unity-worktree1/Modules/UIElements/Core/Scheduler.cs:363)
UnityEngine.UIElements.UIElementsUtility.UnityEngine.UIElements.IUIElementsUtility.UpdateSchedulers () (at C:/Unity/Source/unity-worktree1/Modules/UIElements/Core/UIElementsUtility.cs:278)
UnityEngine.UIElements.UIEventRegistration.UpdateSchedulers () (at C:/Unity/Source/unity-worktree1/Modules/UIElements/Core/UIElementsUtility.cs:108)
UnityEditor.RetainedMode.UpdateSchedulers () (at C:/Unity/Source/unity-worktree1/Modules/UIElementsEditor/RetainedMode.cs:57)
{noformat}