Since the TLD .box is available and using Pi-Hole as DNS Server and NOT as DHCP Server in combination with AVM Fritz!Box all local Domains get an fritz.box as local Domain. Even if using conditional forwarding and never forward non FQDNs and also never forward reverse lookup for local IP‘s its ending up with a lots of reverse lookups.
So I found that the optional local Domain in conditional forwarding in this case is mandatory.
I don’t know if there is a bug, but if not you should change
„You can also specify a local domain name (like
fritz.box ) to ensure queries to devices ending in your local domain name will not leave your network, however, this is optional.“
Of course AVM has simply to add a dot behind box like
That should prevent the problem, but they know it and don’t fix it