Not all contacs synced "because it violates local access rules"

I use Nextcloud 22.2.0 in Docker v20.10.3-1239 Container (Port forwarding 6080 to 80). Database MariaDB 10 v10.3.29-1038 (not in Docker Container, but Synology package). PHP version 7.4.18-0114. PC Client is KDE Kontact (Kubuntu Linux)

I created a calendar in Nextcoud and set up CardDAV Sync with IP_OF_NAS:6080 in the PC client. Then I entered addresses with the PC Client and imported a *.vcf file in the synced address book with the Client.

Now I discovered that not all contacts are available in Nextcloud! I have imported 155 contacts, in Nextcloud 35 are shown as “not grouped” - “all” is not counted.

When I log into Nextcloud as an admin, I find under Logging:

no app in context Host IP_OF_NAS was not connected to because it violates local access rules

Waht are these “local access rules”?

What am I doing wrong?

Btw: with calDAV I didn’t discovered any problems yet.