Local DHCPv4 custom DNS is not used

[Roemer]

Hello

I have a fairly standard OPNSense box. I use quite some services which are available from the internet like "myservice.mydomain.com" which goes to an nginx-container which forwards to the right service. From external this works perfectly. Now to use the same while in the LAN, I use a custom DNS Server which translates "myservice.mydomain.com" into the LAN IP of the nginx-container.
For this, I added my LAN-DNS-IP into Services -> DHCPv4 -> [LAN] -> DNS servers
This actually worked now for almost a week somehow (but seemed strange as some custom entries from my DNS didn't work) but now it stopped working at all. When I now use "myservice.mydomain.com" from the LAN, I get "A potential DNS Rebind attack has been detected." Also if I ping "myservice.mydomain.com" from LAN, I get my WAN address. It seems as if my custom DNS is entirely skipped.

What could be the issue? What am I missing? I read about "Reflection for port forwards" and "Reflection for 1:1" which in the end would lead my connection to WAN and back so I don't want that, I want to directly go to the correct LAN address instead of doing a round trip to WAN.

Many thanks for your help.

[Roemer]

I just found out that when I do an nslookup, I see my opnsense as Server and its ipv6 as address. Could my issue be that it uses ipv6 now for some reason (whereas it used v4 earlier on)?

Edit1: Ok, I disabled ipv6 on my PC and now everything works again! So what is the best I should do? Disable all ipv6 in opnsense? Or somehow disable DNS via ipv6? Or somehow give the ipv6 of my DNS server to DHCPv6?

[Roemer]

I am still suffering from this issue. I disabled Unbound DNS for now which also seems to fix the issue but I am unsure if that is the right way to do it. ANy help would still be very appreciated.