I use nextcloud contacts to store my carddav addressbook. If I only modify a postal address from nextcloud webui or from cardbook plugin for thunderbird or from carddav plugin for roundcube, the modification is successfully synchronized. Every apps will see the new postal address. Davdroid won’t, it seems if postal address was the only modification, davdroid won’t update the contact.
I use davdroid-1.9.10, this bug happens since I use this wonderful app (about 3 years ago).
If this is really a bug, I hope it will be fix soon.