Hi,
So far so good.
My latest “Not Set” was sent on 2020-12-08, the patch was made on the same day. Next day I got the “set” in that days Status Checks Change Notice email. All five of status checks after this fix was installed, have been successful e.g. I haven’t received any “Not Set” notifications after I added “max-recursion-queries 100;” to /etc/bind/named.conf.options.