I'm having some issues with Pi-hole and DNS queries I believe that is causing some weird issues on my network.
Pi-hole has been running for a couple of years now on a Pi4/4GB running Buster dedicated to the task.
The problems I am having are intermittent & varied;
Sometimes pages in the browser (Edge on PC & Safari on Mac/iOS) are very slow on opening and sometimes don't open at all. I have seen an error message on Edge mentioning a DNS issue and thought I took a screenshot but I can't find it.
I have another Pi4/4GB dedicated to feeding FR24, FA, RB24 and ADSBExchange and a couple of times over the weekend it stopped sending data to all of the VR sites and I couldn't even display the data locally.
Another example is if I use the 9to5 Mac app on my iPhone I can read any of the articles but when I click on Comments I do not see any comments on the article at all. If I switch off wi-fi on my phone and use 4G and then click back on the same Comments button I can read all of the comments on that same article.
Again over the weekend I had these and other Pi's drop off the network along with some hardware devices most but not all of which have a static IP address.
A reboot of my PoE switch that also powers all 6 Pi's, 3 WAP's and other devices seemed to temporarily resolve the problem but then it comes back again.
In my DrayTek router I did have both Primary & Secondary DNS Servers set to the same 192.168.0.xxx internal IP address of Pi-hole but over the weekend I removed the secondary to leave it blank and I notice now on some devices the Secondary instead of showing internal Pi-hole IP address is displaying an external IP address from my ISP. Not sure what do set for the best here?
Pi-hole is set to use Cloudflare (DNSSEC) and is set to never forward non-FQDN A and AAAA queries and is not acting as a DHCP Server.
It is showing 1 notification against Pi-hole diagnosis but when clicking into it there are no errors shown?
I don't know where else to look or what to do apart from generating & sending a debug log so I have already taken the liberty of doing this and my debug token is https://tricorder.pi-hole.net/td2Izrkj/
Strangely I done a pihole- up followed by sudo reboot only a day or so ago and yet I see all three elements; Pihole, FTL & web Interface are showing as can be updated?
Any help or advice would be greatly appreciated to steer me towards resolving(!) this intermittent issue.
Thanks & kind regards,