macOS 11.6 BigSur causes heavy traffic for Calendar/Contacts sync

Hi all,

I encounter heavy traffic load on my server, issued by CalDAV/CardDAV sync from one specific Mac.

Steps to reproduce

  1. Client macOS 11.6.1 BigSur
  2. macOS Addressbook and Calendar Apps connected via CalDAV/CardDAV with owncloud for syncing

Expected behaviour

Sync should run smoothly without causing heavy server loads

Actual behaviour

about 200 MB of traffic daily just for Card-/CalDAV syncs which exceeds serverlimits

Server configuration

Operating system: Debian 10

Web server: Apache

Database: 10.3.31-MariaDB

PHP version: 7.4.25

ownCloud version: (see ownCloud admin page) 10.8.0

Updated from an older ownCloud or fresh install:

Where did you install ownCloud from:

Signing status (ownCloud 9.0 and above):

No errors have been found.

The content of config/config.php:

List of activated apps:

  • Admin Config Report
  • Deleted Files
  • Share Files
  • Update Notification
  • Versions
  • Activity
  • Calendar
  • Collaborative Tags
  • Comments
  • Contacts
  • First Run Wizard
  • Gallery
  • Impersonate
  • Market
  • Media Viewer
  • Notifications
  • PDF Viewer
  • Text Editor

Are you using external storage, if yes which one: local/smb/sftp/…


Are you using encryption: yes/no


Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/…


Client configuration


CardDAV, CalDAV build in

Operating system:
macOS 11.6.1 BigSur


Web server error log

tons of entries like:

PROPFIND /remote.php/dav/addressbooks/users/xx/contacts/

all attached to

macOS/11.6 (20G165) AddressBookCore/2452.7

(meanwhile updated to 11.6.1 - no change)

Thanks for any advice

regards Stefan

Problem is still persistant. Any idea anyone?

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