I am getting results with your description of the work. One thing is that you should change the Task type to User Task, but for the basic test case this should not matter.
Can you click on the BPMN2 button in the footer and show the BPMN2 generated so we can test locally?
jBPM Designer uses the jbpm-simulation project you mentioned. jbpm-simulation has moved to jbpm 6 pom already however in Designer we are using still a version which has depends on previous version so don't think that's the issue.
I'd like to get to the bottom of this asap, so if you can help us reproduce that would help a lot.
Thanks.