Vuforia crashes unity when scripts recompiled while running

Vuforia SDK Version: 9.8.8 - Description with steps to reproduce: Windows 10, 64-bit MSVC 2019 16.9.5 Vuforia 9.8.8 Unity 2020.3.8f1 LTS Steps: --- 1. In a scene with Vuforia in it (see note below), press play in the Unity editor. 2. While the editor is in play mode, edit a C# "script" in VS. 3. Switch focus back to the Unity editor. It will recompile the scripts. 4. Stop playback. 5. Start playback again. Expected Behavior: --- No issues. Actual Behavior: --- Note: Not sure what setup causes this, but in my scene there is a single ReferenceImageTarget and Vuforia is set up to use WEBCAM play mode. As soon as the scripts are recompiled (step 3), the following error appears in the console: NullReferenceException: Object reference not set to an instance of an object Vuforia.VideoBackgroundBehaviour.OnDestroy () (at :0) On stopping playback (step 4), nothing of interest happens. However, when restarting playback (step 5), one of two things happens (not sure what determines the difference): About 50% of the time the game screen is replaced with a "Vuforia Initialization Error" ("INIT ERROR: Failed to initialize Vuforia Engine"). When that happens, sometimes you can try again, sometimes not, but the editor becomes generally unstable. About 50% of the time, though, Unity just crashes right away (contact me for logs, not available right now). Log for Vuforia Initialization Error: AR:ERROR: 2021-05-17 14:22:14: Vuforia is already initialized. You need to deinitialize before initializing again. Vuforia initialization failed UnityEngine.Debug:LogError (object) Vuforia.VuforiaRuntime:CheckInitStatus (Vuforia.VuforiaUnity/InitError) Vuforia.VuforiaRuntime:InitInternal () Vuforia.VuforiaRuntime:InitVuforia () Vuforia.VuforiaRuntime:VuforiaInitialization () Vuforia Engine initialization failed: INIT_ERROR INIT ERROR Failed to initialize Vuforia Engine. UnityEngine.Debug:LogError (object) DefaultInitializationErrorHandlerInternal:SetErrorCode (Vuforia.VuforiaUnity/InitError) DefaultInitializationErrorHandlerInternal:OnVuforiaInitializationError (Vuforia.VuforiaUnity/InitError) System.Reflection.MonoMethod:Invoke (object,System.Reflection.BindingFlags,System.Reflection.Binder,object[],System.Globalization.CultureInfo) System.Reflection.MethodBase:Invoke (object,object[]) System.Delegate:DynamicInvokeImpl (object[]) System.MulticastDelegate:DynamicInvokeImpl (object[]) System.Delegate:DynamicInvoke (object[]) Vuforia.DelegateHelper:InvokeDelegate (System.Delegate,object[]) Vuforia.DelegateHelper:InvokeWithExceptionHandling (System.Action`1,Vuforia.VuforiaUnity/InitError) Vuforia.VuforiaRuntime:CheckInitStatus (Vuforia.VuforiaUnity/InitError) Vuforia.VuforiaRuntime:InitInternal () Vuforia.VuforiaRuntime:InitVuforia () Vuforia.VuforiaRuntime:VuforiaInitialization () NullReferenceException: Object reference not set to an instance of an object at UnityEditor.PropertyHandler.IsArrayReorderable (UnityEditor.SerializedProperty property) [0x0005b] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.PropertyHandler.UseReorderabelListControl (UnityEditor.SerializedProperty property) [0x00008] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.PropertyHandler.GetHeight (UnityEditor.SerializedProperty property, UnityEngine.GUIContent label, System.Boolean includeChildren) [0x00059] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.EditorGUI.GetPropertyHeightInternal (UnityEditor.SerializedProperty property, UnityEngine.GUIContent label, System.Boolean includeChildren) [0x00007] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.EditorGUI.GetPropertyHeight (UnityEditor.SerializedProperty property, UnityEngine.GUIContent label, System.Boolean includeChildren) [0x00001] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.Editor.CanBeExpandedViaAFoldoutWithoutUpdate () [0x00036] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.UIElements.EditorElement.UpdateInspectorVisibility () [0x00007] in :0 at UnityEditor.UIElements.EditorElement.Init () [0x000d2] in :0 at UnityEditor.UIElements.EditorElement..ctor (System.Int32 editorIndex, UnityEditor.IPropertyView iw, System.Boolean isCulled) [0x00034] in :0 at UnityEditor.EditorUIServiceImpl.CreateEditorElement (System.Int32 editorIndex, UnityEditor.IPropertyView iw, System.String title) [0x00000] in <5f5866ec908d4054a9597064f39dbbac>:0 at UnityEditor.PropertyEditor.DrawEditors (UnityEditor.Editor[] editors) [0x002e4] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.PropertyEditor.RebuildContentsContainers () [0x00119] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.InspectorWindow.RedrawFromNative () [0x00012] in <015079d9a4ea4f97b4381e694d2310c1>:0 NullReferenceException: Object reference not set to an instance of an object at UnityEditor.PropertyHandler.IsArrayReorderable (UnityEditor.SerializedProperty property) [0x0005b] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.PropertyHandler.UseReorderabelListControl (UnityEditor.SerializedProperty property) [0x00008] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.PropertyHandler.GetHeight (UnityEditor.SerializedProperty property, UnityEngine.GUIContent label, System.Boolean includeChildren) [0x00059] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.EditorGUI.GetPropertyHeightInternal (UnityEditor.SerializedProperty property, UnityEngine.GUIContent label, System.Boolean includeChildren) [0x00007] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.EditorGUI.GetPropertyHeight (UnityEditor.SerializedProperty property, UnityEngine.GUIContent label, System.Boolean includeChildren) [0x00001] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.Editor.CanBeExpandedViaAFoldoutWithoutUpdate () [0x00036] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.UIElements.EditorElement.UpdateInspectorVisibility () [0x00007] in :0 at UnityEditor.UIElements.EditorElement.Init () [0x000d2] in :0 at UnityEditor.UIElements.EditorElement..ctor (System.Int32 editorIndex, UnityEditor.IPropertyView iw, System.Boolean isCulled) [0x00034] in :0 at UnityEditor.EditorUIServiceImpl.CreateEditorElement (System.Int32 editorIndex, UnityEditor.IPropertyView iw, System.String title) [0x00000] in <5f5866ec908d4054a9597064f39dbbac>:0 at UnityEditor.PropertyEditor.DrawEditors (UnityEditor.Editor[] editors) [0x002e4] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.PropertyEditor.RebuildContentsContainers () [0x00119] in <015079d9a4ea4f97b4381e694d2310c1>:0 at UnityEditor.InspectorWindow.RedrawFromNative () [0x00012] in <015079d9a4ea4f97b4381e694d2310c1>:0 Vuforia Engine cannot be started before it is initialized. Please disable Delayed Initializationin the Vuforia configuration or initialize Vuforia manually with the VuforiaRuntime-class. UnityEngine.Debug:LogError (object) Vuforia.VuforiaARController:Start () System.Reflection.MonoMethod:Invoke (object,System.Reflection.BindingFlags,System.Reflection.Binder,object[],System.Globalization.CultureInfo) System.Reflection.MethodBase:Invoke (object,object[]) System.Delegate:DynamicInvokeImpl (object[]) System.MulticastDelegate:DynamicInvokeImpl (object[]) System.Delegate:DynamicInvoke (object[]) Vuforia.DelegateHelper:InvokeDelegate (System.Delegate,object[]) Vuforia.DelegateHelper:InvokeWithExceptionHandling (System.Action) Vuforia.VuforiaBehaviour:Start () - Development OS (Mac OS X, Windows, Linux): Windows 10 - Mobile OS and Version: not applicable - Mobile Device Manufacturer and Model name: not applicable - Do the Vuforia Sample Applications show the same behavior?: Unknown