Yes, one realm at a time worked, but not if I had full sync. For more than year of active using I never had such issue, therefore posted here. Looked weird. I tried from 2 different ISPs, as I have redundant connectivity at home.
Now seems OK, but the updates I make and sync are from me to the server, not vice versa. Might reinstall it on the other machine just to see if this happens again or not.
