Shelly TRV Target Temp is Null


I am completely new to OpenHAB. I have succefully installed it on a Raspberry Pi and added my Shelly TRV.
The Temperature is showing correctly, but target temperatur is showing NULL and I am not able to set it within openHAB.

I clicked everywhere to find something usefull and searched the web for sure. But I am completely lost on why it is NULL and how to track the issue.

Do you have any hint on how I can debug this?

All the best