Appointments cannot be loaded (nor created)

Steps to reproduce

1. Open the Calendar app
2. Optionally, try to create an appointment via "Besprechungsvorschläge +" ("Appointments +")

Expected behavior

1. No appointments related error messages occur after opening the calendar
2. Optionally: appointments can be created, no error messages occur

Actual behavior

1.After opening the Calendar app, an error message occurs (in the upper right corner): "Vorschläge können nicht geladen werden" ("Appointments could not be loaded"?)
2.Optionally, creating an appointment via "Besprechungsvorschläge +" ("Appointments +") ultimately leads to an error message and a contradictory info message: "Vorschlag konnte nicht gespeichert werden" + "Vorschlag 'Test' gespeichert" ("Appointment could not be written" + "Appointment 'Test' written"?)

Calendar app version

6.0.2

CalDAV-clients used

Web-interface integarted within nextcloud

Browser

Firefox 140.4.0esr

Client operating system

Debian

Server operating system

Debian

Web server

Apache

Database engine version

MariaDB

PHP engine version

PHP 8.3

Nextcloud version

32.0.1

Updated from an older installed version or fresh install

Updated from an older version

List of activated apps

Enabled:
  - app_api: 32.0.0
  - appointments: 2.6.1
  - bookmarks: 16.0.0
  - bruteforcesettings: 5.0.0-dev.0
  - calendar: 6.0.2
  - circles: 32.0.0
  - cloud_federation_api: 1.16.0
  - comments: 1.22.0
  - contacts: 8.0.4
  - contactsinteraction: 1.13.1
  - cookbook: 0.11.4
  - dashboard: 7.12.0
  - dav: 1.34.2
  - deck: 1.16.0
  - federatedfilesharing: 1.22.0
  - federation: 1.22.0
  - files: 2.4.0
  - files_downloadlimit: 5.0.0-dev.0
  - files_pdfviewer: 5.0.0-dev.0
  - files_reminders: 1.5.0
  - files_sharing: 1.24.0
  - files_trashbin: 1.22.0
  - files_versions: 1.25.0
  - firstrunwizard: 5.0.0-dev.0
  - logreader: 5.0.0-dev.0
  - lookup_server_connector: 1.20.0
  - mail: 5.5.11
  - nextcloud_announcements: 4.0.0-dev.0
  - notes: 4.12.3
  - notifications: 5.0.0-dev.0
  - oauth2: 1.20.0
  - password_policy: 4.0.0-dev.0
  - passwords: 2025.10.20
  - photos: 5.0.0-dev.1
  - privacy: 4.0.0-dev.0
  - profile: 1.1.0
  - provisioning_api: 1.22.0
  - recommendations: 5.0.0-dev.0
  - related_resources: 3.0.0-dev.0
  - serverinfo: 4.0.0-dev.0
  - settings: 1.15.1
  - sharebymail: 1.22.0
  - spreed: 22.0.1
  - support: 4.0.0-dev.0
  - survey_client: 4.0.0-dev.0
  - systemtags: 1.22.0
  - tables: 1.0.0
  - tasks: 0.17.0
  - text: 6.0.1
  - theming: 2.7.0
  - twofactor_backupcodes: 1.21.0
  - updatenotification: 1.22.0
  - user_ldap: 1.23.0
  - user_status: 1.12.0
  - viewer: 5.0.0-dev.0
  - weather_status: 1.12.0
  - webhook_listeners: 1.3.0
  - workflowengine: 2.14.0
Disabled:
  - activity: 5.0.0-dev.0 (installed 2.11.0)
  - admin_audit: 1.22.0
  - encryption: 2.20.0
  - files_external: 1.24.0
  - files_rightclick: 0.15.1 (installed 1.6.0)
  - suspicious_login: 10.0.0-dev.0
  - twofactor_nextcloud_notification: 6.0.0-dev.0
  - twofactor_totp: 14.0.0
  - whiteboard: 1.4.0 (installed 1.4.0)

Nextcloud configuration

{
    "system": {
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "localhost",
            "***REMOVED SENSITIVE VALUE***"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "32.0.1.2",
        "overwrite.cli.url": "***REMOVED SENSITIVE VALUE***",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "memcache.local": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 6379,
            "timeout": 0
        },
        "filelocking.enabled": true,
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "apps_paths": [
            {
                "path": "\/var\/www\/nextcloud\/apps",
                "url": "\/apps",
                "writable": false
            },
            {
                "path": "\/var\/www\/nextcloud\/apps-3rdparty",
                "url": "\/apps-3rdparty",
                "writable": true
            }
        ],
        "ldapIgnoreNamingRules": false,
        "ldapProviderFactory": "\\OCA\\User_LDAP\\LDAPProviderFactory",
        "maintenance": false,
        "loglevel": 2,
        "defaultapp": "apporder",
        "mail_smtpmode": "smtp",
        "mail_sendmailmode": "smtp",
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "10587",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "theme": "",
        "app_install_overwrite": [
            "passwords",
            "orcid",
            "files_mindmap"
        ],
        "default_phone_region": "DE",
        "data-fingerprint": "ef1cef431a45bbb130424274758d1114",
        "mail_smtpsecure": "tls",
        "mail_smtpauthtype": "PLAIN",
        "mail_smtpauth": 1,
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "maintenance_window_start": 100
    }
}

Web server error log

No apparently related entries.

Log file

No apparently related entries.

Browser log

No apparently related entries.

Additional info

From my point of view, the error messages started to emerge after upgrading nextcloud from 31.0.10 to 32.0.1.

I do not use appointments in the Calendar app at all, so the constantly occurring error messages are a mere annoyance.

I understand that appointments within the Calendar app are based on the Appointments app. I installed the Appointments app only after the error messages occurred trying to provide a possibly missing (and for my part: unnecessary) counterpart for the Calendar app. I tried to reasonably configure the Appointments app but without effect.

So, is this a bug within the Calendar App? Or within the integration of the Appointments app?
Or is there another way to get rid of these error messages, e.g. deactivate/ignore appointments within the Calendar app?
Alternatively: Can somebody point me to a good and brief documentation on how to get appointments with the Calendar and the Appointments apps up and running so that I can subsequently forget about it all again? ;)

Any help is appreciated!

Start by reproducing the error when opening the Calendar app and when using “Besprechungsvorschläge +” with Calendar 6.0.2, Nextcloud 32.0.1, and Appointments 2.6.1. Compare the Calendar/Appointments integration behavior and inspect the browser, application, and web-server logs; done means unused appointments no longer trigger errors and appointment creation reports one consistent result.