Empty contacts for CardDav sync with macOS 10.12.2 Addressbook


I would like to sync my ownCloud contacts via carddav with the Contacts app in macOS Sierra.

I'm using ownCloud 9.1.3 (production) and Contacts.app Version 10.0 (1756.14.6).

Steps to reproduce
The account was added with the following settings:
Password ***
Server https://myserver.net
Path /owncloud/remote.php/dav/addressbooks/users/USERNAME/contacts/
Port 443

Expected behaviour
In the pervious version (El Capitan), contacts synced just fine with this setting. OwnCloud was not updated in the meantime.

Actual behaviour
The addressbook is showing up in the Contacts.app but it is empty.

ownCloud log (data/owncloud.log)
Nothing showing up there.

The apache2 access log is showning:
"OPTIONS /owncloud/remote.php/dav/addressbooks/users/USERNAME/contacts/ HTTP/1.1" 200 1382 "-" "Mac OS X/10.12.2 (16C67) AddressBook/1756.14.6"
"PROPFIND /owncloud/remote.php/dav/addressbooks/users/USERNAME/contacts/ HTTP/1.1" 207 2946 "-" "Mac OS X/10.12.2 (16C67) AddressBook/1756.14.6"

forensics.log is showing
PROPFIND /owncloud/remote.php/dav/addressbooks/users/USERNAME/contacts/ HTTP/1.1|Hostmyserver.net|Accept:/|Brief:t|Authorization:Basic XXXXXX|Accept-Language:en-us|Accept-Encoding:gzip, deflate|Content-Type:text/xml|Content-Length:439|Depth:0|Connection:keep-alive|User-Agent:Mac OS X/10.12.2 (16C67) AddressBook/1756.14.6|Prefer:return=minimal

Depth:0 seems to be the issue. If I try to replicate the call using curl, I get a good XML response but with an empty addressbook. Setting Depth:1 returns all the vcards. I have no idea why the app is requesting depth:0. Maybe it's a first probe but then the actual sync is not executed.

Any ideas what could be the problem? Maybe somebody who has a similar setup but with working synchronization could post their access logs and settings.