Bug Symbol file LoadedFromMemory doesn't match image

On loading project got errors (reload fixes):

(as for nunit it is not even used but always seems to be around as depended on by JetBrains (which I do not use but the plugin is installed by default on all projects...)

Code (JavaScript):

1. Symbol file LoadedFromMemory doesn't match image UnityProject\Library\PackageCache\com.unity.ext.nunit@1.0.0\net35\unity-custom\nunit.framework.dll
2. ReleaseAllScriptCaches did not release all script caches!
3. (Filename: C:\buildslave\unity\build\Runtime/Mono/MonoManager.cpp Line: 1455)
4.  
5. Remaining caches:
6.    UnityEngine.UIElementsModule:UnityEngine.UIElements:StyleSheet
7. Native extension for WindowsStandalone target not found
8. Native extension for iOS target not found
9. Native extension for Android target not found
10. Native extension for OSXStandalone target not found
11. Refreshing native plugins compatible for Editor in 47.52 ms, found 1 plugins.
12. Preloading 0 native plugins for Editor in 0.00 ms.
13. NullReferenceException: Object reference not set to an instance of an object
14.  at UnityEditor.UIElements.UIElementsEditorUtility..cctor () [0x0003d] in <20b79eb59c0f467d8b1106b2110bc953>:0
15. Rethrow as TypeInitializationException: The type initializer for 'UnityEditor.UIElements.UIElementsEditorUtility' threw an exception.
16.  at UnityEditor.UIElements.UIElementsEntryPoint.CreateRoot () [0x00045] in <20b79eb59c0f467d8b1106b2110bc953>:0
17.  at UnityEditor.UIElements.UIElementsEntryPoint.GetRootVisualElement (UnityEditor.EditorWindow window) [0x00011] in <20b79eb59c0f467d8b1106b2110bc953>:0
18.  at UnityEditor.UIElements.DefaultEditorWindowBackend.OnRegisterWindow () [0x0000d] in <20b79eb59c0f467d8b1106b2110bc953>:0
19.  at UnityEditor.UIElements.DefaultEditorWindowBackend.OnCreate (UnityEditor.IWindowModel model) [0x000fe] in <20b79eb59c0f467d8b1106b2110bc953>:0
20.  at UnityEditor.GUIView.set_windowBackend (UnityEditor.IWindowBackend value) [0x0002e] in <20b79eb59c0f467d8b1106b2110bc953>:0
21.  at UnityEditor.GUIView.OnEnable () [0x00008] in <20b79eb59c0f467d8b1106b2110bc953>:0
22.  at UnityEditor.HostView.OnEnable () [0x0001a] in <20b79eb59c0f467d8b1106b2110bc953>:0

 

Not sure if you fixed your problem, but there's a related thread over here with a Unity dev response.

https://forum.unity.com/threads/import-getting-stuck-after-upgrading-to-2021-2-2f1.1208224/