The issue I am facing:
The url raspbian.raspberrypi.org is showing as "BOGUS" which I gather is a failure of DNSSEC. I've noticed a few other URLs do the same over the last few weeks but have not payed attention to them. Turning of the DNSSEC option in pihole of course resolves this. Running the DNSSEC link on the DNS configuration tab of PIHOLE is successful. Using DNSSEC Analyzer - raspbian.raspberrypi.org it "seems" like the results are fine. Direct NSLookup to router is successful, but I'm assuming it doesnt use DNSSEC.
Details about my system:
2 PI Holes in a failover cluster (VIP) point to the router (Ubiquiti Unifi Dream Machine Pro) that in turn points to 18.104.22.168 and 22.214.171.124. Cable modem is in bridge mode.
What I have changed since installing Pi-hole:
No recent changes to PiHOLE, updates are frequent on the router.