Malformed JSON in response body

Hi everyone, 

today I'm asking your help with an issue related to the response messages sent from my production to a client software, such as Postman or SoapUI. 

Issue

In the last few days I've been unable to view the responses received from my production in Postman, even if I was able to do so earlier. I'm sending the request to a remote server reachable via a Putty tunnel.

Postman Test

I'm currently testing this simple POST message: 

{
  "name": "John Doe",
  "email": "johndoe@example.com",
  "age": 30,
  "gender": "Male",
  "height": 175,
  "weight": 70,
  "address": {
    "street": "123 Main Street",
    "city": "Anytown",
    "state": "CA",
    "postalCode": "12345"
  },
  "medications": ["MedicineA", "MedicineB", "MedicineC", "MedicineD"]
}

that returns this error every time: "Error: Parse Error: Expected HTTP/"

From the Postman Console we can see this:

This is a bit strange because I'm expecting a response from the production which has the same message body of the request.

The Business Process that processes the message is quite simple and it possesses only the following methods: 

Method OnRequest(pRequest As EnsLib.HTTP.GenericMessage, Output pResponse As EnsLib.HTTP.GenericMessage) As %Status
{
    Set sc = $$$OK
    Set OriginalStream = pRequest.Stream 
    Set pResponse = ..GenerateRes(OriginalStream)
    Return sc
}

ClassMethod GenerateRes(OriginalStream As %Stream.Object) As EnsLib.HTTP.GenericMessage
{
    // Construct HTTP response
    Set tHttpResponse = ##class(%Net.HttpResponse).%New()
    Set tHttpResponse.ContentType = "application/json"
    // define status line
    Set tHttpResponse.StatusLine = "HTTP/1.1 200 OK"
    // Format the newJson with the correct indentation
    Set jsonFormatter = ##class(%JSON.Formatter).%New()
    Set sc = jsonFormatter.FormatToStream(OriginalStream, .pStream)
    Set pResponse = ##class(EnsLib.HTTP.GenericMessage).%New(pStream,,tHttpResponse)
    Set sc = pResponse.HTTPHeaders.SetAt(tHttpResponse.StatusLine,"STATUSLINE")
    Set sc = pResponse.HTTPHeaders.SetAt(tHttpResponse.ContentType, "Content-Type")
    Return pResponse
}

Examining what it is shown in the Visual Trace, nothing seems to be problematic.

Here is the input message: 

and the following is production's output that is sent back to the client software:

SoapUI Test

I cannot explain why Postman reports that the server returned a malformed message, so I also tried using SoapUI and, in this case, the output is quite interesting: 

As we can see, the Header parameter "Content-Length" is lower than before (now it's 324, earlier it was 330) and the last brace '}' is missing, resulting in a malformed JSON. 

After some research, I've found that other Postman users had a similar issue with the "Content-Length" header, and someone said that he resolved it by removing this header. I've tried but I cannot figure out how to fix this issue with ObjectScript.

Can anyone explain this and provide a solution?

Thank you in advance