Internal URL is not forwarded to the correct port.

[maboxx]

Hello,
I have a problem that I can't explain what it is. Maybe NPM is not the problem at all, but I thought I would ask here first.

I have an OpenWRT router on which I forward the ports 80/443 to my NPM container to 8080/8443.
If I now configure a proxy host with my external domain, this works.

However, if I create a hostname on my OpenWRT router (Turris Omnia), e.g. example.mynetwork.lan and then configure a proxy host with this URL, it does not work.
I create a Proxy Host with example.mynetwork.lan and want it to forward to 192.168.1.9:81. What always happens is that it is forwarded to port 80.

So it all works when I use an external URL but not when I use internal URLs that I create myself on my router. A ping to the URL works and I am also redirected to the correct device but to its default website. Does anyone have an idea?