Hello
It looks like we found a working configuration.
The problem was that winbind was started twice, once by the service centrifydc-samba, and the second time for it's own sake, as the service was active.
So we disabled winbind with systemctl disable winbind.
Now systemctl status centrifydc-samba is reporting an error (it seems to consider that smbd and nmbd are not running), but /etc/init.d/centrifydc-samba status reports all four needed services as runnig.
ps ax is showing winbind, smbd and nmbd running.
Access to shares from windows is working.
smbclient is working without the -k option.
smbclient is not working with -k, but it's not needed.
ssh access to the server for domain users is working, but has always been working since we installed the centrify agent.
As this configuration seems good enough for our needs, we won't investigate further.