Deleted calender events in Thunderbird/Macbook appearing again from nextcloud calender

[c7b3rx]

Steps to reproduce

1. add nextcloud caldav in thunderbird/macbook calender
2. get the calender invitiation from some user and save it into your nextcloud calender using Thunderbird
3. the meeting organizer cancel/delete the meeting and send you the event updates when you click on delete/update, it actually deletes the event in thunderbird/macbook calender but after sometime it appears again, when we checked the event in the nextcloud web calender the event is not there so it's seems like the problem is with nextcloud calender caldav synchronization

Expected behavior

deleted events should not appear again in thunderbird, caldav is not synchronizing properly

Actual behavior

deleted events are not synchronizing with Thunderbird, nextcloud web interface does not have events but nextcloud calender that we added in thunderbird does have event, (no it's not from other/local calender)

Calendar app version

Version 5.5.5, AGPL-licensed

CalDAV-clients used

Thunderbird in Macbook

Browser

No response

Client operating system

No response

Server operating system

No response

Web server

Apache

Database engine version

MariaDB

PHP engine version

PHP 8.1

Nextcloud version

30.0.10

Updated from an older installed version or fresh install

Updated from an older version

List of activated apps

Enabled:
  - activity: 3.0.0
  - admin_audit: 1.20.0
  - app_api: 4.0.6
  - appointments: 2.4.6
  - bookmarks: 15.2.0
  - bruteforcesettings: 3.0.0
  - calendar: 5.5.5
  - circles: 30.0.0
  - cloud_federation_api: 1.13.0
  - comments: 1.20.1
  - contacts: 7.3.2
  - contactsinteraction: 1.11.0
  - dashboard: 7.10.0
  - dav: 1.31.1
  - deck: 1.14.6
  - drawio: 3.0.9
  - external: 5.5.2
  - federatedfilesharing: 1.20.0
  - federation: 1.20.0
  - files: 2.2.0
  - files_antivirus: 5.6.6
  - files_downloadlimit: 3.0.0
  - files_external: 1.22.0
  - files_pdfviewer: 3.0.0
  - files_reminders: 1.3.0
  - files_sharing: 1.22.0
  - files_trashbin: 1.20.1
  - files_versions: 1.23.0
  - firstrunwizard: 3.0.0
  - keeweb: 0.6.21
  - lookup_server_connector: 1.18.0
  - nextcloud_announcements: 2.0.0
  - notifications: 3.0.0
  - oauth2: 1.18.1
  - onlyoffice: 9.10.0
  - password_policy: 2.0.0
  - photos: 3.0.2
  - polls: 8.3.10
  - privacy: 2.0.0
  - provisioning_api: 1.20.0
  - recommendations: 3.0.0
  - related_resources: 1.5.0
  - serverinfo: 2.0.0
  - settings: 1.13.0
  - sharebymail: 1.20.0
  - spreed: 20.1.10
  - support: 2.0.0
  - survey_client: 2.0.0
  - systemtags: 1.20.0
  - text: 4.1.0
  - theming: 2.6.0
  - twofactor_backupcodes: 1.19.0
  - twofactor_totp: 12.0.0-dev
  - updatenotification: 1.20.0
  - user_ldap: 1.21.0
  - user_saml: 7.0.0
  - user_status: 1.10.0
  - viewer: 3.0.0
  - weather_status: 1.10.0
  - webhook_listeners: 1.1.0-dev
  - workflowengine: 2.12.0
Disabled:
  - encryption: 2.18.0
  - files_rightclick: 0.15.1 (installed 1.6.0)
  - files_videoplayer: 1.13.0
  - logreader: 3.0.0 (installed 2.13.0)
  - suspicious_login: 8.0.0
  - twofactor_nextcloud_notification: 4.0.0

Nextcloud configuration

Web server error log

Log file

Browser log

Additional info

No response

[SebastianKrupinski]

Hi @c7b3rx

It seems like TB is not deleting the event in NC.

But to be sure, are there any errors in the NC log?

Also the other issue could be that we have to stages of delete, first delete -> trash bin, second delete -> purged

[c7b3rx]

Hi, thanks for your quick response, actually it's not only about Thunberbird, we also tried it using Macbook's builtin calender

no there are no errors related to calender, can I filter out logs somehow and only see if there's somthing related to Calender

2 stages 🤔 but the thing is in the nextcloud web calender the event doesn't appear anymore

[SebastianKrupinski]

2 stages 🤔 but the thing is in the nextcloud web calender the event doesn't appear anymore

Yes but it should be in the Trashbin, and the "deleted but in trash bin" events are probably still showing in the external client.

[c7b3rx]

nope, trashbin is empty this time I deleted event directly from NC web interface but TB is still showing that event

[SebastianKrupinski]

From the screen capture you posted, you deleted on instance of a recurring event. If TB is still showing the instance that is TB not handling EXDATE according to the RFC.

[c7b3rx]

you mean TB & iPhone calender do not support recurring event deletion?

[matclab]

Same problem here. I've opened a bug report on Thunderbird side : https://bugzilla.mozilla.org/show_bug.cgi?id=2000216

[SebastianKrupinski]

Hi All,

Judging from the screen captures, there are two weekly occurrences that have been deleted, the 6th and 13th. The 13th is not visible on both screen captures, but the 6th is only gone on NC.

This means that there are two instances of EXDATE property. Which is permitted by the iCalendar RFC as EXDATE has a none-or-many cardinality (*).

This means that the client applications are only reading the first EXDATE and ignoring the second instance.

This can be confirmed by downloading the ics of the event and checking for all the instances of EXDATE (if there a two or more lines that start with EXDATE).