simply because it is not good practice to use thread.waits in jbpm actionhandlers. jBPM core is (afaik) single threaded (but performant) because there is the possibility for async actions..
The reason a wait is not good in an action is that you e.g. introduce a waitstate in a state/node/task/...
Thank u Kukeltje for ur fast answer, then i will try to solve my problem without using wait in a node.