Index: lams_monitoring/web/includes/javascript/monitorLesson.js
===================================================================
diff -u -re88a78540d7b5e9e6cdbe66d04fc861f647dc121 -r9df727543960001abd0300a6f3ca8e06fbc77e9f
--- lams_monitoring/web/includes/javascript/monitorLesson.js	(.../monitorLesson.js)	(revision e88a78540d7b5e9e6cdbe66d04fc861f647dc121)
+++ lams_monitoring/web/includes/javascript/monitorLesson.js	(.../monitorLesson.js)	(revision 9df727543960001abd0300a6f3ca8e06fbc77e9f)
@@ -14,6 +14,7 @@
 	learnersTabSortedByProgress = false,
 // currently opened EventSources
 	eventSources = [],
+
 // double tap support
 	tapTimeout = 500,
 	lastTapTime = 0,
@@ -23,7 +24,7 @@
 	popupWidth = 1280,
 	popupHeight = 720,
 
-// cached gate icon data 
+// cached gate icon data
 	gateOpenIconPath   = 'images/svg/gateOpen.svg',
 	gateOpenIconData   = null,
 
@@ -347,7 +348,7 @@
 
 	$('#openImButton').click(openChatWindow);
 
-	//enable renaming of lesson title  
+	//enable renaming of lesson title
 	$('#lesson-name').editable({
 		type: 'text',
 		pk: lessonId,
@@ -856,6 +857,7 @@
 	if (newLessonEndDate) {
 		params.lessonEndDate = newLessonEndDate;
 	}
+
 	$.ajax({
 		url : LAMS_URL + 'monitoring/monitoring/' + method + ".do",
 		data: params,
@@ -1446,8 +1448,6 @@
  * Updates learner progress in sequence tab
  */
 function updateSequenceTab() {
-	clearEventSources();
-
 	drawLessonCompletionChart();
 
 	sequenceCanvas = $('#sequenceCanvas');
@@ -1607,6 +1607,18 @@
 					timeLimitFluxUrl += 'toolContentIds=' + this.toolContentId + '&';
 				});
 
+				// remove from eventSources items which contain "getTimeUpdateFlux" in the URL
+				$.each(eventSources, function(index, eventSource){
+					if (eventSource.url.indexOf('getTimeLimitUpdateFlux.do') > -1) {
+						try {
+							eventSource.close();
+						} catch(e) {
+							console.error("Error while closing Event Source", e);
+						}
+						eventSources.splice(index, 1);
+					}
+				});
+
 				openEventSource(timeLimitFluxUrl,
 					function (event) {
 						if ("doRefresh" == event.data && $('#sequence-tab-content').length === 1){
@@ -2369,7 +2381,7 @@
  * Adds/removes a Learner/Monitor to/from the class.
  */
 function editClassMember(userCheckbox){
-	var data = {
+	var data={
 		'lessonID' : lessonId,
 		'userID'   : userCheckbox.closest('.dialogListItem').attr('userId'),
 		'role'     : userCheckbox.parents('table.dialogTable')
@@ -3087,7 +3099,15 @@
 	});
 }
 
-function openEventSource(url, onMessageFunction) {
+function openEventSource(url, onMessageFunction, skipExisting) {
+	if (skipExisting) {
+		for (let i = 0; i < eventSources.length; i++) {
+			if (eventSources[i].url === url) {
+				return eventSources[i];
+			}
+		}
+	}
+
 	const eventSource = new EventSource(url);
 	eventSources.push(eventSource);
 	eventSource.onmessage = onMessageFunction;