Answer by Graham Dunnett

Unity usually tries to unpack the package into a Temp folder at the root of the Project. So, Temp is a peer of Assets. Inside this temp folder will be a folder called Export Package and inside that a folder with a GUID name. The error occurs when this folder hierarchy cannot be created. Importing Stealth gives me: `Temp/Export Package/6095e79a678cc4db79bd65885cd2d002` Maybe try manually creating the `Temp/Export Package` folder.