Every time you download an upgrade file (has extension .tgz) with Google Chrome, the file gets saved as a .gz file instead of .tgz. This also applies to .img files for Gaia Embedded firmware upgrades.
When you try to use WebUI to upgrade a device, it fails with error message "failed to upload upgrade package, it is not the right file".
When you try to add the package into the SmartUpdate package repository, it fails with the error 'Couldn't add package to repository'