DNS timing out from all the Plus servers
@seebee - I do see similar on my own monitoring, however it seems to have been a relatively new development (last few months). There is a larger piece of work going on behind the scenes that I expect will make the issue 'go away', however I can see if somebody can take a look in the interim.
Remind me next week.
Edit: e.g. this is 12 DNS requests every 300s on my own network: -
@bobpullen Hope this isn't too early for a reminder 
I use smokeping to monitor pings, but I'd never tried it with DNS lookups, so I had a go and I saw overnight between 1.0% and 2.8% loss with the 4 normal DNS, and zero with the 2 SafeGuard ones.
(Raspberry Pi3b, Ethernet, ADSL, IP in 51.9.x.x)
On a tangent - the SD card in my Raspberry Pi failed so I rebuilt it over Xmas. "dig" (which smokeping calls) is giving me results SOMETIMES of 9ms DNS resolution time, which I'd think impossible as I've always seen my ADSL line have an inherent delay of about 13ms (eg pinging gstatic.com or 1.1.1.1 etc).
I'd be tempted to say its something in the recent version of the rPi build. Don't suppose you see "too short" DNS times in your monitoring?
eg
$ dig @212.159.13.49 gstatic.com.
; <<>> DiG 9.16.33-Raspbian <<>> @212.159.13.49 gstatic.com.
...
gstatic.com. 68 IN A 216.58.212.195
;; Query time: 9 msec
;; SERVER: 212.159.13.49#53(212.159.13.49)
...
then
$ dig @212.159.13.49 gstatic.com.
; <<>> DiG 9.16.33-Raspbian <<>> @212.159.13.49 gstatic.com.
...
gstatic.com. 180 IN A 142.250.187.195
;; Query time: 19 msec
;; SERVER: 212.159.13.49#53(212.159.13.49)
...
yet
$ ping -c 100 -q 212.159.13.49
PING 212.159.13.49 (212.159.13.49) 56(84) bytes of data.
--- 212.159.13.49 ping statistics ---
100 packets transmitted, 100 received, 0% packet loss, time 99155ms
rtt min/avg/max/mdev = 12.278/13.911/50.144/3.969 ms
So the smokeping charts are a bit "castellated"!
Zero loss though, which is the important bit.
After looking a bit harder, I'm pretty sure this is a problem with my "dig" command.
It is not related to PN DNS servers, I see the same with 1.1.1.1 for example.
$ for n in {1..30}}; do dig @1.1.1.1 gstatic.com ; done | grep -F time
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 9 msec
;; Query time: 9 msec
;; Query time: 19 msec
;; Query time: 9 msec
;; Query time: 9 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 9 msec
;; Query time: 9 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 9 msec
;; Query time: 9 msec
;; Query time: 19 msec
;; Query time: 19 msec
;; Query time: 9 msec
;; Query time: 19 msecSo dig is only telling me 9ms (which I think is impossible) or 19ms.
If I use the "-u" option to dig, to make it give answers in microseconds instead of milliseconds, it seems to give much more believable results:
$ for n in {1..30}}; do dig -u @1.1.1.1 gstatic.com ; done | grep -F time
;; Query time: 19334 usec
;; Query time: 18390 usec
;; Query time: 18704 usec
;; Query time: 19279 usec
;; Query time: 18448 usec
;; Query time: 18586 usec
;; Query time: 19222 usec
;; Query time: 18407 usec
;; Query time: 18830 usec
;; Query time: 19326 usec
;; Query time: 13941 usec
;; Query time: 15118 usec
;; Query time: 14309 usec
;; Query time: 14134 usec
;; Query time: 14326 usec
;; Query time: 19068 usec
;; Query time: 18895 usec
;; Query time: 19229 usec
;; Query time: 18694 usec
;; Query time: 19321 usec
;; Query time: 18690 usec
;; Query time: 19534 usec
;; Query time: 19450 usec
;; Query time: 18931 usec
;; Query time: 18081 usec
;; Query time: 18632 usec
;; Query time: 18633 usec
;; Query time: 17768 usec
;; Query time: 18800 usec
;; Query time: 18844 usec
So fastest of 13.941 ms and several 14ms, 18ms, 19ms - all seem much more likely.
I only noticed this since rebuilding my Pi to the latest version, so it must be something on my end