@yuanjiashun Thanks for posting the additional information. This is indeed strange. If the error is just displayed after moving the folder and no error is displayed before moving it, it sounds like a bug with Unity's asset management or code project generation system.
If you want to avoid the issue in the future, you could place the spine directories outside the Assets folder so that Unity does not find it (e.g. outside projectname/Assets in projectname/Modules/Spine/) and then add it via the Unity Package Manager as local package, via Add Package from Disk.. as described here for UPM packages.
