Camunda’s mechanism for registering applications with prior process deployments is by default based on the IDs. See https://docs.camunda.org/manual/7.6/user-guide/process-applications/the-processes-xml-deployment-descriptor/#process-application-deployment for a details. The application server log should also show relevant entries when you deploy the second WAR.
You can try giving the deployments distinct names (use the name attribute of the process-archive element in processes.xml) and set the resumeBy property to deployment-name.
Cheers,
Thorben