Task created on Android via DAVx5 shows up twice in the Nextcloud web calendar (as Task and as Event) — duplication is then synced back to Android

[Bruno-FGM]

Steps to reproduce

1.Create a task with a due date on Android, using tasks.org, synced via DAVx5 to Nextcloud.
2.Let it sync to Nextcloud.
3.Open the Nextcloud web Calendar/Agenda view. The same task now shows up twice: once as a Task, once as an Event.
4.Wait for the next sync back to Android (or trigger it manually).
The duplicate now also shows up on the phone.

Expected behavior

A task with a due date should still be visible in the calendar view (that part is fine and useful), but it should appear once, not as two separate entries.

Actual behavior

Task is duplicated as event

Calendar app version

6.5.1

CalDAV-clients used

Davx5

Browser

Firefox 140 ESR

Client operating system

CalyxOS

Server operating system

Ubuntu 24.04

Web server

Apache

Database engine version

MySQL

PHP engine version

PHP 8.4

Nextcloud version

34.0.1

Updated from an older installed version or fresh install

Updated from an older version

List of activated apps

Enabled:
  - activity: 7.0.0
  - admin_audit: 1.24.0
  - app_api: 34.0.0
  - appointments: 2.7.4
  - appstore: 1.0.0
  - bookmarks: 16.2.4
  - bruteforcesettings: 7.0.0
  - calendar: 6.5.1
  - camerarawpreviews: 1.1.2
  - checksum: 2.1.2
  - circles: 34.0.0
  - cloud_federation_api: 1.18.0
  - comments: 1.24.0
  - contacts: 8.7.4
  - contactsinteraction: 1.15.0
  - cookbook: 0.11.9
  - cospend: 4.0.2
  - dashboard: 7.14.0
  - dav: 1.39.0
  - deck: 1.18.2
  - external: 9.0.1
  - federatedfilesharing: 1.24.0
  - federation: 1.24.0
  - files: 2.6.0
  - files_downloadlimit: 5.2.0-dev.0
  - files_external: 1.26.0
  - files_lock: 34.0.0
  - files_pdfviewer: 7.0.0-dev.0
  - files_reminders: 1.7.0
  - files_retention: 5.0.0
  - files_sharing: 1.26.0
  - files_trashbin: 1.24.0
  - files_versions: 1.27.0
  - files_zip: 3.0.0
  - firstrunwizard: 7.0.0-dev.0
  - forms: 5.3.4
  - gestion: 2.8.11
  - gpoddersync: 3.17.0
  - gpxpod: 8.2.1
  - groupfolders: 22.0.3
  - impersonate: 5.0.0
  - libresign: 14.1.0
  - logreader: 7.0.0
  - lookup_server_connector: 1.22.0
  - mail: 5.10.8
  - maps: 1.7.1
  - news: 28.6.0
  - notes: 6.0.1
  - notifications: 7.0.0-dev.1
  - notify_push: 1.3.3
  - oauth2: 1.22.0
  - office: 1.0.0
  - password_policy: 6.0.0-dev.0
  - photos: 7.0.0
  - previewgenerator: 5.14.0
  - privacy: 6.0.0-dev.1
  - profile: 1.3.0
  - provisioning_api: 1.24.0
  - quota_warning: 1.24.0
  - recommendations: 7.0.0
  - related_resources: 5.0.0-dev.0
  - repod: 4.2.1
  - richdocuments: 11.0.1
  - serverinfo: 6.0.0
  - settings: 1.17.0
  - sharebymail: 1.24.0
  - side_menu: 6.0.1
  - spreed: 24.0.2
  - support: 6.0.0
  - survey_client: 6.0.0-dev.0
  - suspicious_login: 12.0.0-dev.0
  - systemtags: 1.24.0
  - tasks: 0.18.1
  - text: 8.0.0
  - theming: 2.9.0
  - twofactor_backupcodes: 1.23.0
  - twofactor_nextcloud_notification: 8.0.0
  - twofactor_totp: 16.0.0
  - user_status: 1.14.0
  - viewer: 7.0.0-dev.0
  - weather_status: 1.14.0
  - webhook_listeners: 1.6.0
  - whiteboard: 1.5.9
  - workflow_script: 5.0.0
  - workflowengine: 2.16.0
Disabled:
  - apporder: 0.15.0 (installed 0.15.0)
  - cloud_py_api: 0.2.0 (installed 0.2.0)
  - documentserver_community: 0.2.4 (installed 0.2.4)
  - domaintheme: 1.0.0 (installed 1.0.0)
  - done: 1.7.0 (installed 1.7.0)
  - encryption: 2.22.0
  - files_fulltextsearch: 33.0.0 (installed 33.0.0)
  - fulltextsearch: 33.0.0 (installed 33.0.0)
  - integration_excalidraw: 3.1.1 (installed 3.1.1)
  - mediadc: 0.4.0 (installed 0.4.0)
  - money: 0.31.0 (installed 0.31.0)
  - nextcloud_announcements: 6.0.0 (installed 1.15.0)
  - recognize: 12.0.0 (installed 12.0.0)
  - theming_customcss: 1.20.0 (installed 1.20.0)
  - user_ldap: 1.25.0

Nextcloud configuration

root@fgmsrv:/usr/local/sbin# sudo nextcloud.occ config:list system
{
    "system": {
        "apps_paths": [
            {
                "path": "\/snap\/nextcloud\/current\/htdocs\/apps",
                "url": "\/apps",
                "writable": false
            },
            {
                "path": "\/var\/snap\/nextcloud\/current\/nextcloud\/extra-apps",
                "url": "\/extra-apps",
                "writable": true
            },
            {
                "path": "\/var\/snap\/nextcloud\/common\/custom_apps",
                "url": "\/custom_apps",
                "writable": true
            }
        ],
        "supportedDatabases": [
            "mysql"
        ],
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 0
        },
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "xxxxxxxxxx.xxx",
            "xxxxxxxxxx.xxx"
        ],
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***",
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "34.0.1.2",
        "overwrite.cli.url": "https:\/\/xxxxxx.xxx\/",
        "htaccess.RewriteBase": "\/",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "maintenance": false,
        "has_rebuilt_cache": true,
        "loglevel": "2",
        "app_install_overwrite": [
            "ocr",
            "cookbook",
            "joplin",
            "podcast",
            "apporder",
            "news",
            "maps",
            "files_rightclick"
        ],
        "logtimezone": "Europe\/Paris",
        "mail_smtpmode": "smtp",
        "mail_smtpsecure": "ssl",
        "mail_sendmailmode": "smtp",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauthtype": "LOGIN",
        "mail_smtpauth": 1,
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "465",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "overwriteprotocol": "https",
        "theme": "",
        "allow_local_remote_servers": true,
        "default_phone_region": "FR",
        "memories.exiftool": "\/var\/snap\/nextcloud\/44391\/nextcloud\/extra-apps\/memories\/bin-ext\/exiftool-amd64-glibc",
        "memories.vod.path": "\/var\/snap\/nextcloud\/44391\/nextcloud\/extra-apps\/memories\/bin-ext\/go-vod-amd64",
        "enabledPreviewProviders": [
            "OC\\Preview\\Image",
            "OC\\Preview\\Movie"
        ],
        "memories.db.triggers.fcu": true,
        "maintenance_window_start": 1,
        "defaultapp": "files",
        "forwarded_for_headers": [
            "HTTP_X_FORWARDED_FOR",
            "HTTP_X-REAL_IP"
        ],
        "log_type": "file",
        "memcache.distributed": "\\OC\\Memcache\\Redis",
        "memcache.local": "\\OC\\Memcache\\APCu",
        "skipped_ips": [
            "192.168.1.0\/24",
            "127.0.0.1",
            "xx.xxx.xxx.xx",
            "xxxxx:xxxxx:xx:xxxx::\/64"
        ],
        "memory_limit": "512M"
    }
}

Web server error log

Log file

nothing seems related...

Browser log

Additional info

It seems it is not happening when creation is done in Nextcloud Task first, or when there is no due date in task...

[odzhychko]

@Bruno-FGM Hi, and thank you for the report.

Before continuing to investigate this, I would need to make sure this is an issue caused by Nextcloud.

Could you provide the following information:

• Does this issue occur when you use other CalDav servers?
  • e.g. Baïkal
• Does this issue occur when you use a different client?
  • e.g. Thunderbird
• Does this issue occur when you use a "CalDAV" account instead of a "DAVx" account in tasks.org?

To help reproduce it would be helpful to know how you created the calendar. Did you create it through

• "New calendar with task list" in the Calendar app?
• "Add List..." in the Task app?
• a third-party CalDAV client?
  • If so, does it you list supports only VTODOs or VTODOs and VEVENTs?

[Bruno-FGM]

Thx for feedback.
Sorry on the move, will check as quicly as I can...