setTempWWsoll does not responde

[Olit2]

Hi,
I have an issue setting warm water temperature via MQTT:
For the room temperature the set command runs perfectly. All readings are also fine, but
for warm water there is no response and

mqtt:
select:

• name: "Warmwasser Soll Temperatur"
  unique_id: "vcontroldgetTempWWsoll"
  #device_class: temperature
  state_topic: "openv/getTempWWSoll"
  #unit_of_measurement: "°C"
  value_template: |-
  {{ value | round(0) }}
  device:
  identifiers: vcontrold
  manufacturer: Viessmann-
  command_topic: "openv/setTempWWSoll"
  options:
  • "40"
  • "52"
  • "53"
  • "54"
  • "55"

I have put the set.TempWWsoll into the Vcontrold configuration.

MQTT pubishes the request (seen with MQTT expolrer,

The protocole shows:
Command: setTempWWsoll
[79] Mon Jun 2 22:44:43 2025 : Error in unit conversion: , terminating
[79] Mon Jun 2 22:44:43 2025 : Error executing setTempWWsoll
SRV ERR: Error in unit conversion: , terminating

Any ideas would be highly welcome.

Cheers
Oli