For the workflow integration Activiti needs ScriptEngineResolvers to handle the script tasks in the workflows. Those are added to the OSGI framework as OSGI services. After system startup eg. there is one associated with the groovy-all bundle ([org.activiti.osgi.Extender$ScriptEngineResolver] groovy-all (14)).
Stopping the groovy-all bundle: the service is removed.
Restarting it: the service is not added again -> it should be handled dynamically without restarting the whole system.