Corrupt database?

I am running ownCloud on a Debian Jessie. I don't know when it started, but since a few updates, the following error occurs regulary:

Steps to reproduce
1. Updating ownCloud

Expected behaviour
The update should finish without errors

Actual behaviour
running the update manually (php occ upgrade) results the following:

Updated to 0.2.7
Update 3rd-party app: calendar
Update 3rd-party app: contacts
notifications: An exception occurred while executing 'CREATE TABLE oc_notifications (notification_id INT AUTO_INCREMENT NOT NULL, app VARCHAR(32) NOT NULL, user VARCHAR(64) NOT NULL, timestamp INT DEFAULT 0 NOT NULL, object_type VARCHAR(64) NOT NULL, object_id VARCHAR(64) NOT NULL, subject VARCHAR(64) NOT NULL, subject_parameters LONGTEXT DEFAULT NULL, message VARCHAR(64) DEFAULT NULL, message_parameters LONGTEXT DEFAULT NULL, link VARCHAR(4000) DEFAULT NULL, actions LONGTEXT DEFAULT NULL, INDEX oc_notifications_app (app), INDEX oc_notifications_user (user), INDEX oc_notifications_timestamp (timestamp), INDEX oc_notifications_object (object_type, object_id), PRIMARY KEY(notification_id)) DEFAULT CHARACTER SET utf8 COLLATE utf8_bin ENGINE = InnoDB':

SQLSTATE[42S01]: Base table or view already exists: 1050 Table 'oc_notifications' already exists
Drop old database tables
28/28 [============================] 100%
Remove old (< 9.0) calendar/contact shares
4/4 [============================] 100%
Fix permissions so avatars can be stored again
2/2 [============================] 100%
Starting code integrity check...
Finished code integrity check
Update successful
Maintenance mode is kept active
Reset log level

Server configuration
Operating system: Debian Jessie
Web server: apache2
Database: sql
PHP version: 5.6.29
ownCloud version (see ownCloud admin page): 9.1.2
Updated from an older ownCloud or fresh install: updated from 9.1.1
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption):

ownCloud log (data/owncloud.log)

Integrity status for oC9+

No errors have been found.

There is an open issue about that available here: