This is why it’s better to use AdGuard only for its DNS blocking capability and not for DNS resolving - use a real resolver like unbound https://en.wikipedia.org/wiki/Unbound_(DNS_server)
IMO it is safer to use a big popular DNS recursor (google, cloudflare, adguard, quad9, etc), use DoT/DoH/DoQ and maybe add some additional filtering on top of it.