Today we got a strange error in production and testing environment: we started a couple of new process instances. We noticed, looking for an error in a call to one of our services, that the new process instance had the same processInstanceId of an older one (the new process had ID 559 but the "last" process instance id was 568)

How it is possible? ProcessInstanceId is not unique? Our process is so simple: only one human task with only 1 value (approved true/false)