The latest available version 8.4.4 has been downloaded.

The installation fails with the following error message:

Unable to install database: Migration class "Concrete\Core\Updater\Migrations\Migrations\Version20160107000000" was not found.

From the folders and files downloaded no such folder Concrete\Core exists. The Migrations section however is found in concrete\src\Updater.

The installation seems to be impossible... what's going on with the downloaded installation package?