When use the WS service task in a process triggered by quartz timer, the following errors are thrown intermittently: Caused by: java.lang.NoSuchMethodException: xxx(xxx) Actually, the soap interface does implement the method it is complaining. This is caused by cxf dynamic client that overrides the class loader set by jbpm. This one-off patch aims to fix the issue in class: org.jbpm.process.workitem.webservice.WebServiceWorkItemHandler The fix is done in https://github.com/droolsjbpm/jbpm/commit/36fb962e1c015b0bd6298c74b1804d790de61be4 which is applied in bpms 6.1.