@devvv4ever ach well, thanks for responding anyway. I realise this thread is old 🙂
I’ve dumped BlackBerry contacts for now and am trying Simple Contacts instead. So far so good!

Hello,

Do you think this is a DAVdroid problem? Did yoo already contact Blackberry support about that?

We got a message from another user using the Blackberry Hub who found the solution:

In the Blackberry contacts app in the preferences check all accounts (also accounts that don’t have any address books). As a server the reporting user is using a mac OSX. Thank you!