Two things:
a) Post your process BPMN2 from the Web Designer (BPMN2 button in the footer section)
b) Try upgrading to the latest designer (http://people.redhat.com/tsurdilo/designer/master) which includes some fixes to the generated BPMN2 of Signal Events and test again. If this still causes issues, then we can look at a possible CommandDelegate problem I think.
Hope this helps.