samba - May 2019 - Naming information cannot be located; server is not operational

Today, I went to run ADUC on a Windows 7 workstation, as I been able to do for
serveral years,
but I got the message, "Naming information cannot be located for the
following reason: The
server is not operational."

However, the server is quite operational. I'm able to authenticate from all
Windows 7/10, Linux
and Mac workstations. I can successfully run getent from a Linux workstations.
The ADUC
workstation can ping the AD/DC server.

Does anyone have any idea why this would suddenly break? Did Microsoft change
something?

AD/DC running Samba 4.8.2 on Linux Slackware64 14.2, kernel 4.4.172.

Thanks, Mark