For years CardDav wasn't working automatically. Used SyncEvolution for a while, but this stopped after I set up a new server and I wasn't able to bring it to work again. So I gave up. I configured CardDav and CalDav with the new server address, but had no success for months and wasn't interested too much to invest more time into that topic.
Now I have Sailfish 184.108.40.206 and Nextcloud 10.0.1, didn't modify my account settings, have CalDav/CarDav still activated, but set to "synchronize manually" and was surprised to notice: whenever I edit a contact in my contact list, the contact will be uploaded immediately to the nextcloud.
Well, this should make me happy - but oftenly the contact double, triple or appears more often in my NextCloud app. Seems it depends on the groups where the contacts were sorted formerly in OwnCloud/Nextcloud and imported back long time ago. Strange enough, because Sailfish doesn't display any group properties. Also, there seems to be a closed loop... I have some contact birthdays now up to 7 times in the calendar app (but no "real" calender events), and some phone numbers also multiple times, not displayed, but in the details list when editing contact details.
I really fear to use the "synchronize" button, anxious if starting a chain reaction blasting both, Sailfish and Nextcloud.
Any hints or clear rules by people who got these both working together properly would be highly appreciated.