Reply error is SERVFAIL. System/setup/install failing?

[srael]

Specs:
I'm running: Latest Ubuntu Server. Latest PiHole, Latest Unbound. Setup using pihole's own guide.

Issue
Woke up this morning to all of my wireless devices reporting no internet connection. As we all know, it is always DNS. I did some testing on my cell and I noticed that when connected to WiFi only some duckduckgo.com would load and yield search yet sites like fast.com or google.com would fail.

I SSH into ubuntu server ran pihole -t and I started to notice entries like:

12:06:22: query[A] www.google.com from 192.168.1.23
12:06:22: forwarded www.google.com to 127.0.0.1#5335
12:06:22: forwarded connectivitycheck.gstatic.com to 127.0.0.1#5335
12:06:22: forwarded www.google.com to 127.0.0.1#5335
12:06:22: reply error is SERVFAIL
12:06:22: reply error is SERVFAIL

I had updated Ubuntu Server LTS the night before but after said update everything was fine. I had rebooted raspberrypi and all. Anyways, I figured the issue was related to Unbound so I jiggled the handle/rebooted raspberrypi to see if things would get fixed. Nothing.

I ran a search and found this thread:

Pihole + Unbound = reply error is SERVFAIL

Hi I`m having trouble with getting pihole to use the 127.0.01#5335 dns. If I use pihile google dns for ip4 and custom Ip6 ( ..1#5335) I get now errors so, something with ip4 is on conflict. As soon as I disable the all pihole dns to the custom 127.0.0.1#5335 dns I get 12:33:37: query[A] www.google.com from (device IP) 12:33:37: forwarded www.google.com to 127.0.0.1 12:33:37: forwarded www.google.com to ::1 12:33:37: forwarded www.google.com to 127.0.0.1 12:33:37: reply error is SERVFAIL …

The solution on said thread:

I did further tests It looks like a Sudo Update that is changing /etc/systemd/resolved.conf FINALL I got it working. Thanks for the mental support.

I guess /etc/systemd/resolved.conf is where the settings for dns-proxy and stubby are set at.
For me this file is nothing but comments #
EDIT: Checking the file again I notice that DNSStubListener=no is enable

I wet to check unbound settings at /etc/unbound/unbound.conf.d/pi-hole.conf and this file is just untouched just like on day 1 when I set it up. So I was back to being lost.

I had to do something so I left. An hour or so later, when I got back home to tackle this issue, to my surprise everything was back up and running without issue. I no longer am seeing reply error is SERVFAIL on pihole -t. and wifi devices show wifi AP having internet access. DNS working normal.

I logged into pihole's web interface to see if it was reporting any errors. Nothing.

What could have been the issue causing reply error is SERVFAIL ?

I'm at a lost.