Deploy API Environment Stop gives Error 500 : Server Error

We are using REST calls from Deploy API. The Environment Stop API is giving the following error. Any clue why this happens. 

com.mendix.modules.microflowengine.MicroflowException: Error calling REST service
    at Deployment.Environment_Stop (CallRest : 'Call REST (POST)')
    at Deployment.IVK_Environment_Stop (SubMicroflow : 'Environment_Stop')

Advanced stacktrace:
    at com.mendix.integration.actions.microflow.RestCallAction.execute(RestCallAction.scala:48)

Caused by: com.mendix.modules.microflowengine.MicroflowException: 500: Server Error
    at Deployment.Environment_Stop (CallRest : 'Call REST (POST)')
    at Deployment.IVK_Environment_Stop (SubMicroflow : 'Environment_Stop')