DNS resolution on pi-hole not working, even though it's working as DNS server

Expected Behaviour:

I'm using pi-hole on a raspberry pi zero 2W, with the default raspberry pi os image. I've installed raspberry pi through the pi-hole script. I'm currently running the following pi-hole versions (pihole -v):

Core version is v6.0.5 (Latest: N/A)
Web version is v6.0.2 (Latest: N/A)
FTL version is v6.0.4 (Latest: N/A)

I run my pi-hole within a VLAN that has access to the internet, but can't access devices on other VLANs. My router is the only client for the pi-hole, as all requests are routed through there.

I'm trying to update pi-hole, but the DNS isn't resolving on the machine itself.

Actual Behaviour:

Today, my DNS stopped working due to the updateGravity.log being to large. On another post I read that you needed to trunctate it, which I did and make the DNS work again. Because I was already cleaning up my pi-hole server, I wanted to update it. When running apt update and pihole -up I got an error that the name couldn't be resolved.

I think that this has something to do with my /etc/resolve.conf file pointing to my routers gateway, which uses the pi-hole as a DNS server. I've tried changing the nameserver directive to a known nameserver, but this value changes back on every reboot. How would I fix the DNS resolution on the pi-hole?

Debug Token:

https://tricorder.pi-hole.net/HPWHSm1H/

The debug log shows /etc/resolv.conf set to use 1.1.1.1 which is good. You don't want Pi-hole to use itself.

The debug log looks clean, what is the exact error you are getting for pihole -up ?

I had to manually set /etc/resolv.conf to 1.1.1.1 to upload the debug log, but it resets when I restarted the pi-hole server. The pihole -up command couldn't update the debian packages and couldn't figure out the OS name.

I figured it out yesterday and forgot to update my post: Originally, I had the WAN DNS server set to my pi-hole within my unifi interface. After changing the WAN DNS servers to other ones and setting up the pi-hole as the DNS server within my VLANs, it was working again. I do think the documentation should be updated to let people know that the default 'one hop away' setting doesn't work if you're using multiple VLANs.

Thanks for your reply!