One process with multiple executions (parallel gateway)

Hi,

I have a workflow that allows users to upload work part by part using forms. Once a part is uploaded, the process moves to the client acceptance and if more parts are needed, it also moves back to the form using a parallel gateway. If the user uploads the second part before the client accepts the first one then I have one process instance with 2 execution waiting for the client acceptance. I tried to send a message to the ‘client revise work’ task but I get this error below. After the process arrives at the parallel gateway, I get 2 tasks. How can I process them one by one if they are waiting on the same process? Must they be joined back at some point?

{
“type”: “RestException”,
“message”: “org.camunda.bpm.engine.MismatchingMessageCorrelationException: ENGINE-13031 Cannot correlate a message with name ‘waiting_client_response’ to a single execution. 2 executions match the correlation keys: CorrelationSet [businessKey=165, processInstanceId=null, processDefinitionId=null, correlationKeys=null, localCorrelationKeys=null, tenantId=null, isTenantIdSet=false]”
}

diagram_4.bpmn (7.6 KB)