Database table not found

If I try to backup I get:

Backup has failed, please review recent log messages.

If I want to view history I get:

The website encountered an unexpected error. Please try again later.

Drupal\Core\Database\DatabaseExceptionWrapper: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'usrdb_xxxxxxxx.backup_db' doesn't exist: SELECT Count(e.eid) AS expression FROM {backup_db} e; Array ( ) in Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (line 128 of core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php).

After installing / before using module I got following warning, that may be also related:

Warning: array_flip(): Can only flip STRING and INTEGER values! in Drupal\Core\Entity\EntityStorageBase->loadMultiple() (line 232 of core/lib/Drupal/Core/Entity/EntityStorageBase.php).

At the moment there is just another problem: I can use website as logged in user but not as anonymous user ... (http 500 error)

Just used D8.0.6