Steps to reproduce the issue

Installed Beta6-dev of 2 December.
Downloaded Deta6-dev update of 3 December.
Joomla! Update - Upload & Update

Expected result

Update to finish normally.

Actual result

HTTP 500 error in libraries/src/Service/Provider/Session.php on line 277

Stack trace
TypeError:
Argument 1 passed to Joomla\CMS\Session\Session::__construct() must be an instance of Joomla\CMS\Session\StorageInterface or null, instance of Joomla\CMS\Session\Storage\JoomlaStorage given, called in C:\www\joomla4\libraries\src\Service\Provider\Session.php on line 277

at C:\www\joomla4\libraries\src\Session\Session.php:39
at Joomla\CMS\Session\Session->__construct(object(JoomlaStorage), object(Dispatcher), array('name' => '8a0e42d3eb2c82772bd1d52ddd5a20c7', 'expire' => 10800))
(C:\www\joomla4\libraries\src\Service\Provider\Session.php:277)
at Joomla\CMS\Service\Provider\Session->buildSession(object(JoomlaStorage), object(AdministratorApplication), object(Dispatcher), array('name' => '8a0e42d3eb2c82772bd1d52ddd5a20c7', 'expire' => 10800))
(C:\www\joomla4\libraries\src\Service\Provider\Session.php:84)
at Joomla\CMS\Service\Provider\Session->Joomla\CMS\Service\Provider{closure}(object(Container))
(C:\www\joomla4\libraries\vendor\joomla\di\src\ContainerResource.php:176)
at Joomla\DI\ContainerResource->getInstance()
(C:\www\joomla4\libraries\vendor\joomla\di\src\Container.php:96)
at Joomla\DI\Container->get('Joomla\Session\SessionInterface')
(C:\www\joomla4\libraries\src\Service\Provider\Application.php:78)
at Joomla\CMS\Service\Provider\Application->Joomla\CMS\Service\Provider{closure}(object(Container))
(C:\www\joomla4\libraries\vendor\joomla\di\src\ContainerResource.php:176)
at Joomla\DI\ContainerResource->getInstance()
(C:\www\joomla4\libraries\vendor\joomla\di\src\Container.php:96)
at Joomla\DI\Container->get('Joomla\CMS\Application\AdministratorApplication')
(C:\www\joomla4\administrator\includes\app.php:57)
at require_once('C:\www\joomla4\administrator\includes\app.php')
(C:\www\joomla4\administrator\index.php:36)

joomla_update.php

#
#Date: 2020-12-02 10:19:58 UTC
#Software: Joomla! 4.0.0-beta6-dev Development [ Mañana ] 27-October-2020 19:54 GMT

#Fields: datetime priority clientip category message
2020-12-02T10:19:58+00:00 INFO 127.0.0.1 update Starting installation of new version.
2020-12-02T10:21:48+00:00 INFO 127.0.0.1 update Finalising installation.
2020-12-02T10:21:49+00:00 INFO 127.0.0.1 update Deleting removed files and folders.
2020-12-02T10:21:55+00:00 INFO 127.0.0.1 update Cleaning up after installation.
2020-12-02T10:21:55+00:00 INFO 127.0.0.1 update Update to version 4.0.0-beta6-dev is complete.
2020-12-03T06:44:18+00:00 INFO 127.0.0.1 update Starting installation of new version.

System information (as much as possible)

Windows 10, Wampserver 3.2.4, Apache 2.4.43a, MySQL 8.0.20, PHP 7.4.13

Additional comments

This error occurs now at both back end and front end, rendering the site unusable.