I believe you are referring to the rebind DNS issue with the fritzbox, do you?
However my Pi-hole is hosted on the internet, not local so I even can't use the fritzbox as upstream DNS.
I summarize the issue: What we figured out is that some or most ads are blocked. When I open a website, taken from the gravity list, it's being displayed (but shown as pihole). When I put this website again on blacklist but add www it's also being blocked. When I remove the www.domain it's displayed again. nslookup only give back correctly 0.0.0.0 (as configured).
I share this hosted Pi-hole with someone. All mentioned domains are blocked for him. He uses IPv6, I am on IPv4.
It might be related to Http:// blocked but not www
but why is it a problem for me and not for others?
Is it really the issue?
What's the workaround?