Switch not updating itself

from my Viessmann heating unit I’m capturing certain values and send them to the REST interface of OH2. The heating unit permits me to turn on heating of warm water by sending a command “set1xWWein” to a web interface. As result, a state “Heating_1xWW_State” in the REST interface changes 0 to EIN and water is heated up until a predefined target temperature is reached. Upon reaching the target temperature, the heating is turned off and the state “Heating_1xWW_State” in the REST interface changes EIN to 0. It is further possible to mannually turn off the heating by sending a command “set1xWWaus” to a web interface.

In the Items if have:

String Heating_1xWW_State						"1x Warmwasser :[%s]" <settings>
String Heating_1xWW_State_onoff						"1x Warmwasser EINAUS"	<settings> {channel="exec:command:f0824e4d:input"}

(the channel is only capable to transmit the value set1xWWein or set1xWWaus to the web interface of the heating system). The Heating_1xWW_State is continuously updated with 0 or EIN from the heating system.

In the sitemap I have:

    		Text item=Heating_1xWW_State label="1x Warmwasser"
    		Switch item=Heating_1xWW_State_onoff label="1x Warmwasser EINAUS" mappings=[set1xWWaus="Aus", set1xWWein="Ein"] 

I can switch on and off the heating, no problem. But what I would like to have is that the switch represents the real current status of Heating_1xWW_State. I.e. after pressing “Ein” it should switch back to “Aus” after the Heating_1xWW_State transitions back from EIN to 0.

How can I do that?

Thank you!!