Exception thrown in SimpleWorkflowManager

I find several execeptions and reports that updates sometimes fail. Not sure these are related (also added JRA-6738)

[atlassian.jira.workflow.SimpleWorkflowManager] An exception occurred
com.opensymphony.workflow.InvalidActionException: Action 5 is invalid
at com.opensymphony.workflow.AbstractWorkflow.doAction(AbstractWorkflow.java:528)
at com.atlassian.jira.workflow.SimpleWorkflowManager.doWorkflowAction(SimpleWorkflowManager.java:176)
at com.atlassian.jira.workflow.WorkflowTransitionUtilImpl.progress(WorkflowTransitionUtilImpl.java:576)
at com.atlassian.jira.web.action.issue.CommentAssignIssue.doExecute(CommentAssignIssue.java:131)
at webwork.action.ActionSupport.execute(ActionSupport.java:153)
at com.atlassian.jira.action.JiraActionSupport.execute(JiraActionSupport.java:46)
at webwork.dispatcher.GenericDispatcher.executeAction(GenericDispatcher.java:131)
at com.atlassian.jira.web.dispatcher.JiraServletDispatcher.service(JiraServletDispatcher.java:186)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:90)
at com.caucho.server.dispatch.ServletFilterChain.doFilter(ServletFilterChain.java:99)
at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:142)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:58)
at com.atlassian.jira.web.filters.SitemeshExcludePathFilter.doFilter(SitemeshExcludePathFilter.java:36)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:168)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:177)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:132)
at com.atlassian.jira.web.filters.ProfilingAndErrorFilter.doFilter(ProfilingAndErrorFilter.java:25)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.jira.web.filters.ActionCleanupDelayFilter.doFilter(ActionCleanupDelayFilter.java:37)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.johnson.filters.JohnsonFilter.doFilter(JohnsonFilter.java:91)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.jira.web.filters.gzip.GzipFilter.doFilter(GzipFilter.java:72)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.core.filters.AbstractEncodingFilter.doFilter(AbstractEncodingFilter.java:36)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:163)
at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:208)
at com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java:259)
at com.caucho.server.port.TcpConnection.run(TcpConnection.java:341)
at com.caucho.util.ThreadPool.runTasks(ThreadPool.java:467)
at com.caucho.util.ThreadPool.run(ThreadPool.java:408)
at java.lang.Thread.run(Thread.java:534)