Program: 69443
Project: 69443
Buggy source:
private void doStart(UserRequest ureq){
  removeAsListenerAndDispose(displayCtrl);
  OLATResourceable ores=OresHelper.createOLATResourceableTypeWithoutCheck("String_Node_Str");
  ThreadLocalUserActivityLogger.addLoggingResourceInfo(LoggingResourceable.wrapBusinessPath(ores));
  WindowControl bwControl=addToHistory(ureq,ores,null);
  RepositoryEntry testEntry=courseNode.getReferencedRepositoryEntry();
  RepositoryEntry courseRe=userCourseEnv.getCourseEnvironment().getCourseGroupManager().getCourseEntry();
  QTI21DeliveryOptions options=getDeliveryOptions(testEntry);
  displayCtrl=new AssessmentTestDisplayController(ureq,bwControl,this,testEntry,courseRe,courseNode.getIdent(),options);
  listenTo(displayCtrl);
  if (displayCtrl.isTerminated()) {
  }
 else {
    displayContainerController=new LayoutMain3ColsController(ureq,getWindowControl(),displayCtrl);
    listenTo(displayContainerController);
    Long courseResId=userCourseEnv.getCourseEnvironment().getCourseResourceableId();
    ICourse course=CourseFactory.loadCourse(courseResId);
    RepositoryEntry courseRepositoryEntry=course.getCourseEnvironment().getCourseGroupManager().getCourseEntry();
    Panel empty=new Panel("String_Node_Str");
    Controller courseCloser=new DisposedCourseRestartController(ureq,getWindowControl(),courseRepositoryEntry);
    Controller disposedRestartController=new LayoutMain3ColsController(ureq,getWindowControl(),empty,courseCloser.getInitialComponent(),"String_Node_Str" + courseResId);
    displayContainerController.setDisposedMessageController(disposedRestartController);
    boolean fullWindow=config.getBooleanSafe(IQEditController.CONFIG_FULLWINDOW);
    if (fullWindow) {
      displayContainerController.setAsFullscreen(ureq);
    }
    displayContainerController.activate();
    assessmentStopped=false;
    singleUserEventCenter.registerFor(this,getIdentity(),assessmentInstanceOres);
    singleUserEventCenter.fireEventToListenersOf(new AssessmentEvent(AssessmentEvent.TYPE.STARTED,ureq.getUserSession()),assessmentEventOres);
  }
}

Fixed version (ground truth):
private void doStart(UserRequest ureq){
  removeAsListenerAndDispose(displayCtrl);
  OLATResourceable ores=OresHelper.createOLATResourceableTypeWithoutCheck("String_Node_Str");
  ThreadLocalUserActivityLogger.addLoggingResourceInfo(LoggingResourceable.wrapBusinessPath(ores));
  WindowControl bwControl=addToHistory(ureq,ores,null);
  RepositoryEntry courseRe=userCourseEnv.getCourseEnvironment().getCourseGroupManager().getCourseEntry();
  displayCtrl=new AssessmentTestDisplayController(ureq,bwControl,this,testEntry,courseRe,courseNode.getIdent(),deliveryOptions);
  listenTo(displayCtrl);
  if (displayCtrl.isTerminated()) {
  }
 else {
    displayContainerController=new LayoutMain3ColsController(ureq,getWindowControl(),displayCtrl);
    listenTo(displayContainerController);
    Panel empty=new Panel("String_Node_Str");
    Controller courseCloser=new DisposedCourseRestartController(ureq,getWindowControl(),courseRe);
    Controller disposedRestartController=new LayoutMain3ColsController(ureq,getWindowControl(),empty,courseCloser.getInitialComponent(),"String_Node_Str");
    displayContainerController.setDisposedMessageController(disposedRestartController);
    boolean fullWindow=config.getBooleanSafe(IQEditController.CONFIG_FULLWINDOW);
    if (fullWindow) {
      displayContainerController.setAsFullscreen(ureq);
    }
    displayContainerController.activate();
    assessmentStopped=false;
    singleUserEventCenter.registerFor(this,getIdentity(),assessmentInstanceOres);
    singleUserEventCenter.fireEventToListenersOf(new AssessmentEvent(AssessmentEvent.TYPE.STARTED,ureq.getUserSession()),assessmentEventOres);
  }
}