HS.FHIRServer.Interop.Service returning error status code and OperationOutcome

I'm using this service to create a FHIR facade. 

I want to return OperationOutcome to the calling application when I detect an error. 

My code at present is :

set quickStreamOut=##class(HS.SDA3.QuickStream).%New()

set operationOutcome = ##class(HS.FHIR.DTL.vR4.Model.Resource.OperationOutcome).%New()

s issue = ##class(HS.FHIR.DTL.vR4.Model.Element.OperationOutcome.issue).%New()

s issue.severity = "error"

s issue.code = "exception"

s issue.details = ##class(HS.FHIR.DTL.vR4.Model.Datatype.CodeableConcept).%New()

try {

s issue.details.text = exception.DisplayString()

} catch ex {

s issue.details.text = "Unknown exception"

}

d operationOutcome.issue.Insert(issue)

$$$ThrowOnError(quickStreamOut.CopyFrom(operationOutcome.ToJSON()))

set response = ##class(HS.FHIRServer.Interop.Response).%New()

set response.Response.ResponseFormatCode="JSON"

set response.Response.Status=200

set response.ContentType="application/fhir+json"

set response.CharSet = "utf8"

set response.QuickStreamId = quickStreamOut.%Id()

If I change the response code to 422, the calling app doesn't get the OperationOutcome. Instead I get 

The custom error module does not recognize this error.
 

Do I need to implement a custom error?