Nextcloud 19 - User Login not possible

Nextcloud version: 19.0.0 beta 5
Operating system and version: Ubuntu 18.04.4 LTS
Apache or nginx version: Apache/2.4.29
PHP version: PHP 7.3.17-1

Hi there,
I’m facing an issues with the user login of Nextcloud and I hope, someone here could maybe help me out to solve this problem.

I’m not able to login via Webbrowser with a normal user account which I’d created when I was installing Nextcloud (I think in version 13 or 14). I receive the following Error Msg in the Server Protocol (see below).

My admin account works without any problems. Also, when I create a new user account, the login works without any problems.

I’ve tried to change the password for the corrupt user account, with no success of fixing the issue.

Maybe someone here could give me a hint how to fix the old account?

Many thanks in advance!

The output of the Nextcloud log in Admin > Logging:

[index] Error: Exception: Argument 1 passed to OCA\Password_Policy\Compliance\Expiration::entryControl() must be an instance of OCP\IUser, null given, called in /var/www/nextcloud/apps/password_policy/lib/ComplianceService.php on line 95 at <<closure>>

0. /var/www/nextcloud/lib/private/AppFramework/App.php line 136
   OC\AppFramework\Http\Dispatcher->dispatch(OC\Core\Controller\LoginController {}, "tryLogin")
1. /var/www/nextcloud/lib/private/AppFramework/Routing/RouteActionHandler.php line 47
   OC\AppFramework\App::main("OC\\Core\\Controller\\LoginController", "tryLogin", OC\AppFramework\ ... {}, {_route: "core.login.tryLogin"})
2. <<closure>>
   OC\AppFramework\Routing\RouteActionHandler->__invoke({_route: "core.login.tryLogin"})
3. /var/www/nextcloud/lib/private/Route/Router.php line 298
   call_user_func(OC\AppFramework\ ... {}, {_route: "core.login.tryLogin"})
4. /var/www/nextcloud/lib/base.php line 1007
5. /var/www/nextcloud/index.php line 37

POST /login
from [IP] at 2020-05-04T08:13:49+00:00

Solved through an update to NC19.0.0beta7 (where they fixed the password_policy module).