I have been trying to upgrade our application to Drools 5.5 from Drools 5.4. I rebuilt several knowledgeBases containing processes with Drools 5.5, but I can't get them to run. I can get a simple DRL file that does not reference any processes to run just fine. Both the DRL and the KBs use statelessSessions. The program has been used for a couple years, and has been modified to run with Drools 5.1.1, 5.3, 5.4, and now 5.5, and has been supporting processes since Drools 5.3 / jBPM 5.2. Here is the bomb that I get: OpenCDS call to Drools.execute failed with error: Unexpected exception executing action org.jbpm.process.instance.event.DefaultSignalManager$SignalAction@5cd5a2a9 org.drools.common.AbstractWorkingMemory:executeQueuedActions:995 org.drools.common.DefaultAgenda:fireNextItem:1239 org.drools.common.DefaultAgenda:fireAllRules:1456 org.drools.common.AbstractWorkingMemory:fireAllRules:710 org.drools.common.AbstractWorkingMemory:fireAllRules:674 org.drools.impl.StatefulKnowledgeSessionImpl:fireAllRules:230 org.drools.impl.StatelessKnowledgeSessionImpl:execute:278 org.opencds.service.drools.v55.DroolsAdapter:getOneResponse:370 org.opencds.dss.evaluate.EvaluationImpl:evaluate:169 org.opencds.service.TestEvaluationImpl:main:156 org.omg.dss.DSSRuntimeExceptionFault: OpenCDS call to Drools.execute failed with error: Unexpected exception executing action org.jbpm.process.instance.event.DefaultSignalManager$SignalAction@5cd5a2a9 executeQueuedActions fireNextItem fireAllRules fireAllRules fireAllRules fireAllRules execute getOneResponse evaluate main I have single-stepped through the code with Eclipse, but I can't quite figure out what is wrong with my KBs. They ran just fine on Drools 5.4 (although there was a memory leak in Drools with that version), and the only thing I changed was to populate the "probability" value on the BPMN-Diagram (because it wouldn't validate without it). The program builds a command list, and executes it with the following: ExecutionResults results = null; try { results = statelessKnowledgeSession.execute(CommandFactory.newBatchExecution((cmds))); } catch (Exception e) { String err = "OpenCDS call to Drools.execute failed with error: " + e.getMessage(); log.error(err); StackTraceElement elements[] = e.getStackTrace(); for (int i = 0, n = elements.length; i < n; i++) { String detail = elements[i].getClassName() + ":" + elements[i].getMethodName() + ":" + elements[i].getLineNumber(); log.error(detail); err += "\n" + elements[i].getMethodName(); } throw new DSSRuntimeExceptionFault(err); } Has anybody seen this error before? Thanks for any ideas or suggestions! -- des