Shelly 2.5 not sending http-commands to itself

I'm going crazy over this. I have a Shelly 2.5 wired up but want to have Switch 2 trigger a toggle on Relay 1 (which is directly connected to anthoer switch). So Switch 2 Button Type is set to "Detached" and the button switched on URL is configured to http://192.168.42.90/relay/0/?turn=toggle, where 192.168.42.90 is the Shelly's IP.

This does not work. However, what is puzzling me is what does work:

If I change the URL to http://192.168.42.1/relay/0/?turn=toggle, where 192.168.42.1 is a server running an nginx web server, I see a line in the nginx server's log:

192.168.42.90 - - [10/Dec/2022:17:03:50 +0100] "GET /relay/0/?turn=toggle HTTP/1.1" 404 169 "-" "-"

If I run "curl http://192.168.42.90/relay/0/?turn=toggle" from that same host (where nginx is running), the relay is toggled.

So, sending action works, receiving actions works, but sending actions to itself, for some reason, does not work.

Anyone with any idea what is wrong?

Thanks! That was my initial configuration, but as it was not working, I was not sure whether the shelly had a loopback device, so I switched to the actual IP.

Great, so I guess, my device is Jinxed, that's all. It works with the IP of any other Shelly in the house not just this one.

I now changed Switch-Mode to Cycle (which does what I want as relay 2 is not connected), but still puzzled.