@leondante Hello again.
This looks very much like an upstream updates issue we have seen a number of times and revolves around a major update that took place upstream that changed samba major versions and occasionally ends up with the new version half installed with a broken nmbd element:
Take a look at the following forum thread:
where @Haioken resolved something that looks to be the same as your are experiencing:
Also it may be helpful to paste the output of the suggested command in that error message.
See how you get on with that thread
Hope that helps.