Several of context variables may not return a value if a custom context type is being used

${request.mainpart} 
${request.parts[0] 
${request.parts.0.body} 
${request.parts.0.mainpart} 
${request.parts[1] 
${request.parts.1.body} 
${request.parts.1.mainpart} 

Release:
Component: APIGTW

Add the cluster wide property contentType.otherTextualTypes with the value of custom context type being used. 

Example: application/vnd.lotsys.motors.event.request-1+json