Nobody any idea? I know the information is scarce, but if I knew more I would be much closer to the solution.
What I know so far:
Mac A: Master
Mac B: S.er.va.nt
Data on Mac A isn't synced to CloudKit while data from CloudKit is synced to Mac B and the other way round. When I completely delete the app on Mac A (including database file called xxx.sqlite), syncing starts again on Mac A, but all Data I added meantime on Mac A is gone. Restoring only database file (xxx.sqlite) on Mac A, syncing stopps again on Mac A.
So in my opinion, there must be a flag inside the sqlite-file or there's a special character in database I accidentally used, so syncing won't start.
It would be very nice, if somebody can help.
And if I had one wish, dear fairy, it would be very nice if maybe a developer from Apple could comment on it. I know: nice try, but one can wish.