Failed CardDav sync with due to 'invalid format'

Has anybody successfully synced contacts with via CardDav? Each of my contacts fail sync. How can I further troubleshoot this?

“Sync of item xxxx failed due to the following error: One of the identified items was in an invalid format”

I’m using EMClient v7.1.30794.0

Can you upgrade to the latest version at and see if the problem persists.