WSO2 ESB does not return ERROR_MESSAGE, but it does inside ERROR_RESPONSE - wso2

Question

I am implementing failure sequence for a service in WSO2 EBS, but it just never return ERROR_MESSAGE or other failure properties like ERROR_REASON.
However it does return this fields inside $ctx:ERROR_RESPONSE.
how come is this possible? any clue how to extract this fields outside ERROR_RESPONSE?
<?xml version="1.0" encoding="UTF-8"?>
<sequence name="Failure" statistics="enable" trace="enable" xmlns="http://ws.apache.org/ns/synapse">
<log description="Log error details in case of failure" level="full">
<property name="MESSAGE" value="An unexpected error occurred."/>
<property expression="$ctx:ERROR_CODE" name="ERROR_CODE"/>
<property expression="$ctx:ERROR_RESPONSE" name="ERROR_RESPONSE"/>
<property expression="$ctx:ERROR_MESSAGE" name="ERROR_MESSAGE"/>
</log>
<payloadFactory description="Build payload with error information" media-type="json">
<format>
{
"status": "An unexpected error occurred.",
"code": $1,
"response": $2,
"message": $3,
}
</format>
<args>
<arg evaluator="xml" expression="$ctx:ERROR_CODE"/>
<arg evaluator="xml" expression="$ctx:ERROR_RESPONSE"/>
<arg evaluator="xml" expression="$ctx:ERROR_MESSAGE"/>
</args>
</payloadFactory>
<respond description="Respond back to client with custom error payload"/>
</sequence>