has anyone succedd with a POST/PUT towards NPrinting API with a request body?

I can start tasks and do other stuff that doesn't require a request body, but f.ex. PUT /users/{id}/groups does not work.

I have all other stuff working (im quite sure at least) like Origin, X-HTTP-Method-Override, Cookie but I receive a 400 - "Malformed parameters in body" when i try the following in the request body field in QvRestConnector;

{

   "groupIds": "guid-of-a-group"

}

Have tried both directly in Rest Connector setup, with a "with connection" including a replace(vBodyString,'"',chr(34) & chr(34)) and postman.

Am i doing something wrong or is the API just not working as expected?

Running Feb-18 release btw.

Br Johan