No writing permissions when there are several groups with different permissions at shared calenders

[nova-os]

Steps to reproduce

1. Add two groups. One has write and read, the other has readonly
2. Add one user to both groups

Expected behaviour

User should be able to edit the calender.

Actual behaviour

User can only view calender and has no permission to write.

Server configuration

Operating system:
linux
Web server:
apache
Database:
mysql
PHP version:
5.6
Server version: (see your admin page)
10.0.1
Calendar version: (see the apps page)
1.4.0
Updated from an older installed version or fresh install:
fresh installed
Signing status (ownCloud/Nextcloud 9.0 and above):

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

No errors have been found.
List of activated apps:

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your instance's installation folder

Enabled:

• activity: 2.3.2

• calendar: 1.4.0

• comments: 1.0.0

• contacts: 1.4.0.0

• dav: 1.0.1

• federatedfilesharing: 1.0.1

• federation: 1.0.1

• files: 1.5.2

• files_pdfviewer: 0.8.1

• files_sharing: 1.0.0

• files_texteditor: 2.1

• files_trashbin: 1.0.0

• files_versions: 1.3.0

• files_videoplayer: 0.9.8

• firstrunwizard: 1.1

• gallery: 15.0.0

• notifications: 0.3.0

• password_policy: 1.0.0

• provisioning_api: 1.0.0

• serverinfo: 1.1.1

• survey_client: 0.1.5

• systemtags: 1.0.2

• theming: 1.0.1

• updatenotification: 1.0.1

• workflowengine: 1.0.1
  Disabled:

• admin_audit

• encryption

• external

• files_accesscontrol

• files_automatedtagging

• files_external

• files_retention

• templateeditor

• user_external

• user_ldap

• user_saml
  The content of config/config.php:

  {
  "system": {
  "instanceid": "ocimemixhyjj",
  "passwordsalt": "REMOVED SENSITIVE VALUE",
  "secret": "REMOVED SENSITIVE VALUE",
  "trusted_domains": [
  "xxx.de"
  ],
  "datadirectory": "/usr/www/users/wolkek/data",
  "overwrite.cli.url": "http://xxx.de",
  "dbtype": "mysql",
  "version": "9.1.1.5",
  "dbname": "wolkek_db3",
  "dbhost": "localhost",
  "dbport": "",
  "dbtableprefix": "oc_",
  "dbuser": "REMOVED SENSITIVE VALUE",
  "dbpassword": "REMOVED SENSITIVE VALUE",
  "logtimezone": "UTC",
  "installed": true
  }
  }

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/...
no

LDAP configuration (delete this part if not used)

With access to your command line run e.g.:
sudo -u www-data php occ ldap:show-config
from within your instance's installation folder

Without access to your command line download the data/owncloud.db to your local
computer or access your SQL server remotely and run the select query:
SELECT * FROM `oc_appconfig` WHERE `appid` = 'user_ldap';

Eventually replace sensitive data as the name/IP-address of your LDAP server or groups.

Client configuration

Browser:
chrome
Operating system:
macOS
CalDAV-clients:
Nextcloud

Logs

Web server error log

Insert your webserver log here

Log file (data/owncloud.log)

Insert your ownCloud.log file here

Browser log

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log 
c) ...

notify @nova-tb

[MorrisJobke]

cc @georgehrke @rullzer @schiessle

[georgehrke]

Duplicate,

@nickvergessen fixed this already.

[georgehrke]

original bug: #3677

fix: #3678

was also backported to Nextcloud 11