[GSS] Error "Could not initialize class org.kie.internal.utils.ServiceRegistryImpl" appear with sample business process

There is no clear steps which can reproduce the issue systematically.. But this seems to happen more frequently on Windows environment. In the customer's environment, performing Project -> Clear cause/switch the error frequently. Here is steps to reproeude the issue . 1. select [File] → [New] → [other] 2. select [jBPM project] in [jBPM] and then click [Next] 3. input project name 4. select [a more advanced process including human tasks and persistence] and then click 5. select [jBPM 6 or above] and then click [Finish] 6. open sample.bpmn => in case of Linux, you may not see any error but in case of Windows, you may see either of these errors. (in my case, I see SOLVER error at this point.) 7. run business process as JUnit test 8. in top menu, perform [Project] -> [Clean] => reported error would appear If you perform [Project] -> [Clean] again, error would switch to the other one.