I have been running Activiti engine for the last 3 months in production environment with success but strangely enough there have been two instances when duplicate tasks were created. I am wondering if it is caused by some bug in the engine or some outside factor. My setup has a cluster of 3 tomcat servers. Any clues to resolve this issue will be appreciated. The flow picture is attached here just for reference. The duplicate tasks were created at Impact Assessment and Final Impact Assessment tasks once each time. Both these tasks are multi-instance tasks.