[] printing/print_cups.c:cups_job_submit(656)
Unable to print file to - client-error-bad-request


And the printing is stopped, of course.

The solution is simple:

LANG=en_US.UTF-8 /etc/init.d/samba restart

In short:
/var/log/cups/error_log shows a lot of

E [] Unsupported character set "iso-8859-1"!

CUPS requires UTF-8.
In the case of default login in Debian, the console IS in UTF-8, but is not if you have customized it and use `su` for administrative tasks.

C’ia.