DT Global Inbox Sync issue one way

I am using DEVONthink on four devices:

1. DT 3.9.6 / Sonoma 14.4.1 on Mac Mini (main work place)
2. DTTG on iPad on the road
3. DTTG on iPhone
4. DT 3.9.6 / Monterey 12.7.2 on Macbook

Sync method iCloud CloudKit

Syncing works fine with iPad, iPhone and Macbook.

Problem with Mac Mini global inbox:
New items from iPad, iPhone or Macbook global inbox are synced to Mac Mini.
New items in the global inbox of the Mac mini are not synced to the other devices.

Syncyng other group works fine in both direction.

I checked every database and the global inbox (repair and integrity).

Any Idea?

TIA
Herb