Partially non-editable calendar entry → with invitation of external guest → created with Fossify Calendar

Steps to reproduce

1. Create calendar entry with Fossify Calendar
2. Add an external email address for an invitation
3. Sync with Nextcloud server v32.0.5 via DAVx5 v4.5.7.1-ose
4. Open calendar entry with the Webinterface by Nextcloud

Expected behavior

1. Normal entry to edit anything and entirely like other calendar entries
   AND
2. The external participant receives an email with invitation

Actual behavior

1. You can only edit a few things. For example the time is fixed. Have a look at this screenshot:

AND

2. The invited person doesn't get an email.

Calendar app version

6.1.5

CalDAV-clients used

DAVx5

Browser

x

Client operating system

x

Server operating system

No response

Web server

Apache

Database engine version

MySQL

PHP engine version

PHP 8.4

Nextcloud version

32.0.5

Updated from an older installed version or fresh install

None

List of activated apps

- activity: 5.0.0-dev.0
  - bookmarks: 16.0.1
  - bruteforcesettings: 5.0.0-dev.0
  - calendar: 6.1.5
  - cloud_federation_api: 1.16.0
  - comments: 1.22.0
  - contacts: 8.2.1
  - contactsinteraction: 1.13.1
  - dav: 1.34.2
  - encryption: 2.20.0
  - event_update_notification: 2.7.0
  - federatedfilesharing: 1.22.0
  - federation: 1.22.0
  - files: 2.4.0
  - files_downloadlimit: 5.0.0-dev.0
  - files_linkeditor: 1.1.23
  - files_reminders: 1.5.0
  - files_sharing: 1.24.1
  - files_trashbin: 1.22.0
  - files_versions: 1.25.0
  - forms: 5.2.3
  - integration_openstreetmap: 3.0.0
  - logreader: 5.0.0-dev.0
  - lookup_server_connector: 1.20.0
  - memories: 7.7.0
  - notes: 4.12.4
  - notifications: 5.0.0-dev.0
  - oauth2: 1.20.0
  - password_policy: 4.0.0-dev.0
  - passwords: 2025.12.21
  - photos: 5.0.0-dev.1
  - privacy: 4.0.0-dev.0
  - profile: 1.1.0
  - provisioning_api: 1.22.0
  - related_resources: 3.0.0-dev.0
  - serverinfo: 4.0.0-dev.0
  - settings: 1.15.1
  - sharebymail: 1.22.0
  - side_menu: 5.1.3
  - socialsharing_email: 4.0.1
  - suspicious_login: 10.0.0-dev.0
  - systemtags: 1.22.0
  - tasks: 0.17.1
  - text: 6.0.1
  - theming: 2.7.0
  - twofactor_backupcodes: 1.21.0
  - twofactor_nextcloud_notification: 6.0.0-dev.0
  - twofactor_totp: 14.0.0
  - updatenotification: 1.22.0
  - viewer: 5.0.0-dev.0
  - webhook_listeners: 1.3.0
  - workflowengine: 2.14.0

Nextcloud configuration

{
    "system": {
        "memcache.local": "\\OC\\Memcache\\APCu",
        "memcache.locking": "\\OC\\Memcache\\APCu",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "maintenance_window_start": 100,
        "trusted_domains": [
            "localhost",
            "*.XYZ"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "skeletondirectory": "",
        "dbtype": "mysql",
        "version": "32.0.5.0",
        "overwrite.cli.url": "https:\/\/XYZ",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "allow_user_to_change_display_name": false,
        "config_preset": 1,
        "default_language": "de_DE",
        "default_locale": "de_DE",
        "force_language": "de_DE",
        "force_locale": "de_DE",
        "default_phone_region": "de",
        "htaccess.RewriteBase": "\/",
        "mail_smtpmode": "smtp",
        "mail_sendmailmode": "smtp",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtptimeout": 30,
        "mail_smtpauth": true,
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "465",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "mail_send_plaintext_only": true,
        "trashbin_retention_obligation": "auto, 365",
        "versions_retention_obligation": "auto, 365",
        "loglevel": 2,
        "logtimezone": "Europe\/Berlin",
        "knowledgebaseenabled": false,
        "remember_login_cookie_lifetime": 2419200,
        "session_lifetime": 604800,
        "lost_password_link": "disabled",
        "overwriteprotocol": "https",
        "appcodechecker": true,
        "simpleSignUpLink.shown": false,
        "forbidden_filename_basenames": [
            "con",
            "prn",
            "aux",
            "nul",
            "com0",
            "com1",
            "com2",
            "com3",
            "com4",
            "com5",
            "com6",
            "com7",
            "com8",
            "com9",
            "com\u00b9",
            "com\u00b2",
            "com\u00b3",
            "lpt0",
            "lpt1",
            "lpt2",
            "lpt3",
            "lpt4",
            "lpt5",
            "lpt6",
            "lpt7",
            "lpt8",
            "lpt9",
            "lpt\u00b9",
            "lpt\u00b2",
            "lpt\u00b3"
        ],
        "forbidden_filename_characters": [
            "<",
            ">",
            ":",
            "\"",
            "|",
            "?",
            "*",
            "\\",
            "\/"
        ],
        "forbidden_filename_extensions": [
            " ",
            ".",
            ".filepart",
            ".part"
        ],
        "twofactor_enforced": "true",
        "twofactor_enforced_groups": [],
        "twofactor_enforced_excluded_groups": [],
        "maintenance": false,
        "defaultapp": "calendar,contacts",
        "theme": "",
        "app_install_overwrite": [],
        "mail_smtpsecure": "ssl",
        "memories.db.triggers.fcu": true,
        "memories.exiftool": "XYZ\/apps\/memories\/bin-ext\/exiftool-amd64-glibc",
        "memories.vod.path": "XYZ\/apps\/memories\/bin-ext\/go-vod-amd64",
        "preview_max_x": 1024,
        "preview_max_y": 1024,
        "enabledPreviewProviders": [
            "OC\\Preview\\Image",
            "OC\\Preview\\HEIC",
            "OC\\Preview\\TIFF",
            "OC\\Preview\\Movie"
        ],
        "updater.secret": "***REMOVED SENSITIVE VALUE***"
    }
}

Web server error log

Log file

Browser log

Additional info

No response

Reproduce the event flow using Fossify Calendar, DAVx5, and the Nextcloud web interface with an external invitee. Start by tracing how the calendar app handles CalDAV events with external attendees and how the web interface determines editable fields and sends invitations. Done means the event remains fully editable and the external participant receives the invitation.