I also noticed this message on one of my servers but I wasn’t able to find the cause yet, see also [Samba] Could not convert SID S-0-0, error is NT_STATUS_NONE_MAPPED
Could it be that there was an old domain PDC.LOCAL? Are there other domain controllers in the network?
Let’s check the set winbind options:
root@home:~# runagent -m samba1 podman exec -t samba-dc testparm -s | grep winbind
winbindd:use external pipes = true
A possible workaround could be to filter those log entries, see also NS8 - /dev/mapper/vg_var-lv_var is at 86% - #5 by mrmarkuz