HTTPMessage Empty value in Stream

I have an operation with the EnsLib.HTTP.GenericOperation class. This operation sends the following json message:

<HTTPMessage xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:s="http://www.w3.org/2001/XMLSchema">

<Stream>

{ "resourceType":"Bundle", "id":"ec5ffdbe-3739-47e6-81e4-2b0498e99fb8", "meta":[ { "lastUpdated":"2020-09-20T15:04:17.764+02:00" }], "type":"searchset", "total":"1", "link":[ { "relation":"self", "url":"https:\/\/xxx:5665\/api\/fhir\/DSTU3\/CarePlan?encounter=861241" }], "entry":[ { "fullUrl":"https:\/\/xxx:5665\/api\/fhir\/DSTU3\/CarePlan\/23104", "resource":[ { "resourceType":"CarePlan", "id":"23104", "identifier":[ { "system":"urn:hcis:mrns", "value":"23104" }] }], "addresses":[ { "reference":"Condition\/76741" }], "subject":[ { "reference":"Patient\/10055765" }] }] }

</Stream><Type>

CG

</Type>

</HTTPMessage>

I send it to the same namespace (localhost: 9980) to a service with the EnsLib.REST.GenericService class. When I receive the message stream is empty. Why?

<HTTPMessage xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:s="http://www.w3.org/2001/XMLSchema">

<Stream></Stream>

<Type>BG</Type>

<HTTPHeaders><HTTPHeadersItem HTTPHeadersKey="CONTENT-LENGTH">0</HTTPHeadersItem><HTTPHeadersItem HTTPHeadersKey="CONTENT-TYPE">text/plain; charset="UTF-8"

</HTTPHeadersItem><HTTPHeadersItem HTTPHeadersKey="StatusLine">HTTP/1.1 500 Internal Server Error</HTTPHeadersItem></HTTPHeaders>

</HTTPMessage>