Pi-hole conflicting with FritzOS 7.26?

[piholeuser3]

Hi, my pi-hole runs on a Raspberry Pi Zero W with Raspbian 10. In my Fritzbox 7490, the pi-hole is configured as primary DNSv4 server and DNS over TSL is activated. Until recently, everything worked like a charm. Things changed after updating my router.

Usually, I update the pi-hole via SSH using

sudo apt-get update && sudo apt-get upgrade -y && pihole -up

Currently this is what happens:

Temporary failure resolving 'raspbian.raspberrypi.org'
unable to access 'GitHub - pi-hole/pi-hole: A black hole for Internet advertisements': Could not resolve host: github.com
Retrieval of supported OS list failed. dig failed with return code 10.
Unable to determine if the detected OS (Raspbian 10) is supported_

I tried uploading the debug token, but this didn't work either:

curl failed, falling back to netcat for transmission.
nc: getaddrinfo for host "tricorder.pi-hole.net" port 9999: Temporary failure in name resolution

Help would be appreciated.

[Bucking_Horn]

This could indeed be a temporary DNS failure, so a simple retry may work.

If it doesn't, you could check the DNS servers your RPi Zero is using:

sudo nano /etc/resolv.conf

Then edit the nameserver line to nameserver 9.9.9.9 or your preferred third party DNS service, save and exit, and retry updating.

[piholeuser3]

Changing the nameserver in resolv.conf fixed the problem.
Thank you very much.