We are coding Plugins for Roundcube.
We noticed that Google stopped to return vcard URL's on a PROPFIND request to ...
https://google.com/m8/carddav/principals/__uids__/user%40gmail.com/lists/default/
Due to this issue Thunderbird/SoGo stopped sync'ing contacts too.
Issue was reported first time 03/28/2013.
Does anyone know a workaround?