contacts birthday remains in calendar after deletion

[Bilemma]

Expected behaviour

After I delete a contact, its birthday entry should be removed from the calendar.

Actual behaviour

recently I noticed some (!) double birthday entrys in my contact's birthday calendar. After I deleted one of these contacts completely, one of the two entrys disappeared from calendar. But the other one is still there and I can't get get rid of it.

Maybe my database is corrupt after updating to the newest versions of owncloud and contacts app. Is there any way to check that?

Server configuration

Operating system: Synology DSM 6.0.2-8451 Update 9 Web server: Apache HTTP Server 2.2 Database:

PHP version: PHP 5.6 ownCloud version: (see ownCloud admin page)

Contacts version: (see ownCloud apps page) 1.5.1 Updated from an older ownCloud or fresh install: updated Signing status (ownCloud 9.0 and above): ?

Login as admin user into your ownCloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results here.

No errors have been found.

List of activated apps: Enabled:

• activity: 2.3.2
• calendar: 1.4.1
• comments: 0.3.0
• contacts: 1.5.1
• dav: 0.2.7
• federatedfilesharing: 0.3.0
• federation: 0.1.0
• files: 1.5.1
• files_pdfviewer: 0.8.1
• files_sharing: 0.10.0
• files_texteditor: 2.1
• files_trashbin: 0.9.0
• files_versions: 1.3.0
• files_videoplayer: 0.9.8
• firstrunwizard: 1.1
• gallery: 15.0.0
• notifications: 0.3.0
• provisioning_api: 0.5.0
• systemtags: 0.3.0
• templateeditor: 0.1
• updatenotification: 0.2.1 Disabled:
• encryption
• external
• files_antivirus
• files_external
• user_external
• user_ldap

The content of config/config.php: $CONFIG = array ( 'trusted_domains' => array ( 0 => 'xyz', 1 => 'xyz.ddns.net', 2 => 'xyz.synology.me', ), 'instanceid' => 'ocjkggqs5hc3', 'datadirectory' => '/volume1/web/owncloud/data', 'overwrite.cli.url' => 'http://xyz/owncloud', 'dbtype' => 'mysql', 'version' => '9.1.3.1', 'dbname' => 'owncloud', 'dbhost' => 'localhost', 'dbtableprefix' => 'oc_', 'dbuser' => 'oc_ownadmin', 'logtimezone' => 'UTC', 'installed' => true, 'theme' => '', 'loglevel' => 2, 'maintenance' => false, 'trashbin_retention_obligation' => 'auto', );

Are you using external storage, if yes which one: local/smb/sftp/... no.

Are you using encryption: yes/no no. Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/... WebDAV: Android DAVDroid; Windows 10 EM Client

Client configuration

Browser: Chrome,( Edge) Operating system: Windows 10 CardDAV-clients: Android DAVDroid; Windows 10 EM Client (only used to correct the groups as described above)

ownCloud log (data/owncloud.log)

I only insert one line as an example, the log file is full of these:

{"reqId":"PFNhGGCynEemxmicEeU1","remoteAddr":"92.226.179.67","app":"PHP","message":"PHP Startup: No such handler: DBA_DEFAULT at Unknown#0","level":3,"time":"2017-02-07T11:46:13+00:00","method":"OPTIONS","url":"/owncloud/remote.php/carddav/principals/myname/","user":"myname"}