Index: lams_common/src/java/org/lamsfoundation/lams/lesson/LearnerProgress.java
===================================================================
RCS file: /usr/local/cvsroot/lams_common/src/java/org/lamsfoundation/lams/lesson/LearnerProgress.java,v
diff -u -r1.25.10.3 -r1.25.10.4
--- lams_common/src/java/org/lamsfoundation/lams/lesson/LearnerProgress.java	11 May 2016 07:07:26 -0000	1.25.10.3
+++ lams_common/src/java/org/lamsfoundation/lams/lesson/LearnerProgress.java	5 Jan 2017 11:19:30 -0000	1.25.10.4
@@ -36,6 +36,7 @@
 import org.apache.commons.lang.builder.EqualsBuilder;
 import org.apache.commons.lang.builder.HashCodeBuilder;
 import org.apache.commons.lang.builder.ToStringBuilder;
+import org.apache.log4j.Logger;
 import org.lamsfoundation.lams.learningdesign.Activity;
 import org.lamsfoundation.lams.learningdesign.ActivityOrderComparator;
 import org.lamsfoundation.lams.learningdesign.ComplexActivity;
@@ -64,6 +65,8 @@
 public class LearnerProgress implements Serializable {
     private static final long serialVersionUID = -7866830317967062822L;
 
+    private static Logger log = Logger.getLogger(LearnerProgress.class);
+
     //---------------------------------------------------------------------
     // Class level constants
     //---------------------------------------------------------------------
@@ -346,17 +349,28 @@
 	// remove activity from current set
 	byte oldState = getProgressState(activity);
 	if (oldState == state) {
+	    log.debug("Progress " + this.getLearnerProgressId() + " does not change state " + state + " of activity "
+		    + activity.getActivityId());
 	    // no real change, forget the rest of the method
 	    return;
 	}
 
 	Date activityStartDate = attemptedActivities.get(activity);
-
+	if (activityStartDate == null) {
+	    log.warn("Progress " + this.getLearnerProgressId() + " found NULL start date of activity "
+		    + activity.getActivityId());
+	}
 	if (oldState == LearnerProgress.ACTIVITY_NOT_ATTEMPTED) {
+	    log.debug("Progress " + this.getLearnerProgressId() + " does not remove not attempted activity "
+		    + activity.getActivityId());
 	    ;
 	} else if (oldState == LearnerProgress.ACTIVITY_ATTEMPTED) {
+	    log.debug("Progress " + this.getLearnerProgressId() + " removes attempted activity "
+		    + activity.getActivityId());
 	    this.attemptedActivities.remove(activity);
 	} else if (oldState == LearnerProgress.ACTIVITY_COMPLETED) {
+	    log.debug("Progress " + this.getLearnerProgressId() + " removes completed activity "
+		    + activity.getActivityId());
 	    this.completedActivities.remove(activity);
 	    if (activity.isComplexActivity()) {
 		ComplexActivity complex = (ComplexActivity) activityDAO
@@ -371,10 +385,16 @@
 
 	// add activity to new set
 	if (state == LearnerProgress.ACTIVITY_NOT_ATTEMPTED) {
+	    log.debug("Progress " + this.getLearnerProgressId() + " does not add not attempted activity "
+		    + activity.getActivityId());
 	    ;
 	} else if (state == LearnerProgress.ACTIVITY_ATTEMPTED) {
+	    log.debug(
+		    "Progress " + this.getLearnerProgressId() + " adds attempted activity " + activity.getActivityId());
 	    this.attemptedActivities.put(activity, new Date());
 	} else if (state == LearnerProgress.ACTIVITY_COMPLETED) {
+	    log.debug(
+		    "Progress " + this.getLearnerProgressId() + " adds completed activity " + activity.getActivityId());
 	    this.completedActivities.put(activity,
 		    new CompletedActivityProgress(this, activity, activityStartDate, new Date()));
 	}
Index: lams_learning/src/java/org/lamsfoundation/lams/learning/service/LearnerService.java
===================================================================
RCS file: /usr/local/cvsroot/lams_learning/src/java/org/lamsfoundation/lams/learning/service/LearnerService.java,v
diff -u -r1.112.2.16 -r1.112.2.17
--- lams_learning/src/java/org/lamsfoundation/lams/learning/service/LearnerService.java	15 Dec 2016 11:48:26 -0000	1.112.2.16
+++ lams_learning/src/java/org/lamsfoundation/lams/learning/service/LearnerService.java	5 Jan 2017 11:19:32 -0000	1.112.2.17
@@ -604,9 +604,9 @@
      * @return the updated learner progress
      */
     @Override
-    public void completeActivity(Integer learnerId, Activity activity, LearnerProgress progress) {
+    public synchronized void completeActivity(Integer learnerId, Activity activity, LearnerProgress progress) {
 	// load the progress again from DB
-	progress = learnerProgressDAO.getLearnerProgress(progress.getLearnerProgressId());
+	// progress = learnerProgressDAO.getLearnerProgress(progress.getLearnerProgressId());
 	if (progress.getCompletedActivities().keySet().contains(activity)) {
 	    // progress was already updated by another thread, so prevent double processing
 	    return;