In this case after updating a Centos 7.3 installation to 7.4 suddenly a customer old printer cant store scan jobs in a samba share.
After enable verbose log in samba configuring option
log level = 2
we saw some entries like
ntlm_password_check: NTLMv1 passwords NOT PERMITTED for user printeruser
unfortunately our printer was to old and maker does not offer support. we need to allow ntlm authentication in samba enabling ntlm auth option
security = user passdb backend = tdbsam map to guest= Bad User ntlm auth = yes