Possible fix for download race condition.

problem_builder/data_export.py

@@ -172,6 +172,8 @@ class DataExportBlock(XBlock):
             return {'error': 'permission denied'}
         from .tasks import export_data as export_data_task  # Import here since this is edX LMS specific
         self._delete_export()
+        # Make sure we nail down our state before sending off an asynchronous task.
+        self.save()
         if not username:
             user_id = None
         else:

problem_builder/public/js/data_export.js

@@ -26,7 +26,7 @@ function DataExportBlock(runtime, element) {
     }
 
     function updateStatus(newStatus) {
-        var statusChanged = newStatus !== status;
+        var statusChanged = ! _.isEqual(newStatus, status);
         status = newStatus;
         if (status.export_pending) {
             // Keep polling for status updates when an export is running.