Contact changes with TBSync via Nextcloud generate duplicate entries in iPhone

[Martin511]

Your environment

TbSync version: 3.0.1 Thunderbird version: 91.2.0 (64-Bit)

Expected behavior

Editing a contact in TB addressbook (synced with Nextcloud and then also with iPhone) should just update the existing entry.

Actual behavior

Editing a contact in TB addressbook updates the entry in Nextcloud but generates a double entry in iPhone.

Steps to reproduce

...

Hello,

I have the following constellation:

Nextcloud contacts synced with Thunderbird TBSync and also with iPhone (no iCloud, only direct path to Nextcloud server).

My problem:

No matter where I edit a contact - basically everything works fine and is synchronised on the other 2 devices.
BUT: If I edit a contact in Thunderbird (no matter whether TBSync or Cardbook, no matter whether 78 or 91), then an additional contact is created in the iPhone address book (which then contains the change).
In Nextcloud, the existing contact is updated as desired.

I just can't figure out what the reason for this could be.

So:

Edit contact in iPhone: Nextcloud and TB are updated

Edit contact in Nextcloud: iPhone and TB are updated

Edit contact in Thunderbird: Nextcloud is updated, but an additional entry is created in the iPhone.