Copyright © 2026 Unity Technologies
Steps to reproduce:
1. Create a new Unity project using Universal 3D Template
2. Import provided "Audio.mp3" file into the Assets folder
3. Select the .mp3 in the Project Browser
4. Press Ctrl+D (Cmd+D on macOS) and quickly duplicate it 2-3 times
5. Observe the Console window
Actual results: "UnityException" and "InvalidOperationException" errors are thrown in the Console window
Expected results: No errors are thrown in the Console window
Reproducible with versions: 6000.0.78f1, 6000.3.20f1, 6000.5.4f1, 6000.6.0b5, 6000.7.0a3
Tested on (OS): macOS Tahoe 26.5.2 (M1)
UnityException: Calls to "AssetDatabase.CopyAsset" are restricted during asset importing. Please make sure this function is not called from ScriptedImporters or PostProcessors, as it is a source of non-determinism. UnityEditor.AssetDatabase.CopyAsset (System.String path, System.String newPath) (at <47dfb82687474f36ae3f51f095598680>:0) UnityEditor.AssetClipboardUtility.PasteCopiedAssets (System.String destination) (at /Users/bokken/build/output/unity/unity/Editor/Mono/ProjectBrowser/AssetClipboardUtility.cs:164) UnityEditor.AssetClipboardUtility.DuplicateAssets (System.Collections.Generic.IEnumerable`1[T] assets) (at /Users/bokken/build/output/unity/unity/Editor/Mono/ProjectBrowser/AssetClipboardUtility.cs:79) UnityEditor.AssetClipboardUtility.DuplicateSelectedAssets () (at /Users/bokken/build/output/unity/unity/Editor/Mono/ProjectBrowser/AssetClipboardUtility.cs:24) UnityEditor.ProjectBrowser.HandleCommandEvents () (at /Users/bokken/build/output/unity/unity/Editor/Mono/ProjectBrowser/ProjectBrowser.cs:2044) UnityEditor.ProjectBrowser.OnGUI () (at /Users/bokken/build/output/unity/unity/Editor/Mono/ProjectBrowser/ProjectBrowser.cs:2303) UnityEditor.HostView.InvokeOnGUI (UnityEngine.Rect onGUIPosition) (at /Users/bokken/build/output/unity/unity/Editor/Mono/HostView.cs:532) UnityEditor.DockArea.DrawView (UnityEngine.Rect dockAreaRect) (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/DockArea.cs:411) UnityEditor.DockArea.OldOnGUI () (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/DockArea.cs:402) 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:416) UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEventInternal (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:782)
InvalidOperationException: Collection was modified; enumeration operation may not execute. System.Collections.Generic.HashSet`1+Enumerator[T].MoveNext () (at <ed6c7d6212d3440ba66942901750c59a>:0) UnityEditor.AssetClipboardUtility.PasteCopiedAssets (System.String destination) (at /Users/bokken/build/output/unity/unity/Editor/Mono/ProjectBrowser/AssetClipboardUtility.cs:112) UnityEditor.AssetClipboardUtility.DuplicateAssets (System.Collections.Generic.IEnumerable`1[T] assets) (at /Users/bokken/build/output/unity/unity/Editor/Mono/ProjectBrowser/AssetClipboardUtility.cs:79) UnityEditor.AssetClipboardUtility.DuplicateSelectedAssets () (at /Users/bokken/build/output/unity/unity/Editor/Mono/ProjectBrowser/AssetClipboardUtility.cs:24) UnityEditor.ProjectBrowser.HandleCommandEvents () (at /Users/bokken/build/output/unity/unity/Editor/Mono/ProjectBrowser/ProjectBrowser.cs:2044) UnityEditor.ProjectBrowser.OnGUI () (at /Users/bokken/build/output/unity/unity/Editor/Mono/ProjectBrowser/ProjectBrowser.cs:2303) UnityEditor.HostView.InvokeOnGUI (UnityEngine.Rect onGUIPosition) (at /Users/bokken/build/output/unity/unity/Editor/Mono/HostView.cs:532) UnityEditor.DockArea.DrawView (UnityEngine.Rect dockAreaRect) (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/DockArea.cs:411) UnityEditor.DockArea.OldOnGUI () (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/DockArea.cs:402) 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:416) UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEventInternal (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:782) 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:719)
Issues you vote on will appear here