A question though - are you sure this is not normal
behavior ?
Most of my research on the net (with caution I know) seems
to suggest that ssh disconnection after authentication because
of /bin/false is normal ?
Yes, it is normal. A user with /bin/false as his ahell should not be
able to login. These days www-data has /bin/false too, which caught
be out, until I changed it back.