Thank you very much Nick, for the excellent explanations and for all the work you're doing for all of us.
Trying to be helpful, here are my 2 cents:

/code
yum reinstall app-samba
systemctl restart winbind.service
...
journalctl -xe
.. systemd[1]: Unit winbind.service entered failed state.
.. systemd[1]: winbind.service failed.
.. servicewatch[22102]: restarting winbind
.. polkitd[919]: Registered Authentication Agent for unix-process:24734:8819234 (system bus name :1.18811 [/usr/bin/pkttyagent --notify-fd 5 --fallback],
.. systemd[1]: winbind.service: main process exited, code=exited, status=1/FAILURE
.. systemd[1]: Failed to start Samba Winbind Daemon.
-- Subject: Unit winbind.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit winbind.service has failed.
--
-- The result is failed.
.. systemd[1]: Unit winbind.service entered failed state.
.. systemd[1]: winbind.service failed.
.. polkitd[919]: Unregistered Authentication Agent for unix-process:24734:8819234 (system bus name :1.18811, object path /org/freedesktop/PolicyKit1/Authe
/code

Hope this helps