It seems the issue lies in how the Fritz!Box handles DNS resolution. While it forwards most DNS queries correctly, it may not properly resolve specific external domains like "rasppi1.hilmar-preusse.de" due to its configuration or caching behavior. You can try manually setting the provider's DNS server (e.g., 2001:a60::53:1) on your device to bypass the Fritz!Box for DNS resolution. For advanced setups or if you need a more reliable solution, consider using a dedicated dns server for better performance and control. HostNoc can provide robust solutions for hosting and DNS needs. Learn everything you need to know about DNS Hierarchy here: https://www.hostnoc.com/dns-hierarchy-everything-you-need-to-know/