I’m sorry- my bad. tried to use homeassistant in a docker container (only to integrate my Aqara FP2 and Cupra Born) and started it with default setting
--net=host
which exposes all host ports to the docker container. This seemed to mess up my Coap Openhab setup. When I stop the docker container Openhab and Shelly Coap is working fine again.
Sorry again and thanks to everyone who helped me out.