DSS Error with JSON output configured in the reult

I have a problem with my DSS service and it's been frustrating as I can't find any answer to my problems. My service has a sqlserver data source and mapped configured my output as JSON, and when testing the service with the content type application/json I'm getting an error. Below is the dss carbon logs. I encountered this before and the solution was to enable Escape Non Printable Characters, however even if I enabled it I'm still getting the error below. Please please help.

Caused by: DS Fault Message: Error in 'SQLQuery.processNormalQuery'
DS Code: DATABASE_ERROR
Source Data Service:-
Name: FTE
Location: /FTE.dbs
Description: N/A
Default Namespace: http://ift.tt/18X1brw
Current Request Name: _getusers_login
Current Params: {login=103}
Nested Exception:-
DS Fault Message: Error in XML generation at StaticOutputElement.execute
DS Code: UNKNOWN_ERROR
Nested Exception:-
javax.xml.stream.XMLStreamException: Invalid Staring element


        at org.wso2.carbon.dataservices.core.description.query.SQLQuery.processNormalQuery(SQLQuery.java:864)
        at org.wso2.carbon.dataservices.core.description.query.SQLQuery.runQuery(SQLQuery.java:2290)
        at org.wso2.carbon.dataservices.core.description.query.Query.execute(Query.java:282)
        at org.wso2.carbon.dataservices.core.engine.CallQuery.executeElement(CallQuery.java:179)
        at org.wso2.carbon.dataservices.core.engine.CallQueryGroup.executeElement(CallQueryGroup.java:111)
        at org.wso2.carbon.dataservices.core.engine.OutputElement.execute(OutputElement.java:89)
        at org.wso2.carbon.dataservices.core.description.resource.Resource.execute(Resource.java:67)
        at org.wso2.carbon.dataservices.core.engine.DataService.invoke(DataService.java:462)
        at org.wso2.carbon.dataservices.core.engine.DSOMDataSource.execute(DSOMDataSource.java:96)
        ... 46 more
Caused by: DS Fault Message: Error in XML generation at StaticOutputElement.execute
DS Code: UNKNOWN_ERROR
Nested Exception:-
javax.xml.stream.XMLStreamException: Invalid Staring element

        at org.wso2.carbon.dataservices.core.engine.StaticOutputElement.executeElement(StaticOutputElement.java:258)
        at org.wso2.carbon.dataservices.core.engine.OutputElement.execute(OutputElement.java:89)
        at org.wso2.carbon.dataservices.core.engine.OutputElementGroup.executeElement(OutputElementGroup.java:106)
        at org.wso2.carbon.dataservices.core.engine.OutputElement.execute(OutputElement.java:89)
        at org.wso2.carbon.dataservices.core.description.query.Query.writeResultEntry(Query.java:396)
        at org.wso2.carbon.dataservices.core.description.query.SQLQuery.processNormalQuery(SQLQuery.java:857)
        ... 54 more
Caused by: javax.xml.stream.XMLStreamException: Invalid Staring element
        at org.apache.axis2.json.gson.GsonXMLStreamWriter.writeStartElement(GsonXMLStreamWriter.java:239)
        at org.wso2.carbon.dataservices.core.engine.XMLWriterHelper.writeResultElement(XMLWriterHelper.java:144)
        at org.wso2.carbon.dataservices.core.engine.StaticOutputElement.executeElement(StaticOutputElement.java:250)
        ... 59 more