diff --git a/mod/assign/backup/moodle2/restore_assign_stepslib.php b/mod/assign/backup/moodle2/restore_assign_stepslib.php
index 0987c53e531..d4ba0a56a18 100644
--- a/mod/assign/backup/moodle2/restore_assign_stepslib.php
+++ b/mod/assign/backup/moodle2/restore_assign_stepslib.php
@@ -387,6 +387,12 @@ class restore_assign_activity_structure_step extends restore_activity_structure_
             return;
         }
 
+        // Skip group overrides if we are not restoring groupinfo.
+        $groupinfo = $this->get_setting_value('groups');
+        if (!$groupinfo && !is_null($data->groupid)) {
+            return;
+        }
+
         $data->assignid = $this->get_new_parentid('assign');
 
         if (!is_null($data->userid)) {
diff --git a/mod/assign/lib.php b/mod/assign/lib.php
index e1872d30938..36336d6247e 100644
--- a/mod/assign/lib.php
+++ b/mod/assign/lib.php
@@ -260,6 +260,9 @@ function assign_update_events($assign, $override = null) {
             $conds['userid'] = $override->userid;
         } else if (isset($override->groupid)) {
             $conds['groupid'] = $override->groupid;
+        } else {
+            // This is not a valid override, it may have been left from a bad import or restore.
+            $conds['groupid'] = $conds['userid'] = 0;
         }
     }
     $oldevents = $DB->get_records('event', $conds, 'id ASC');
diff --git a/mod/assign/upgradelib.php b/mod/assign/upgradelib.php
index d0bbc45a93a..10ab600920a 100644
--- a/mod/assign/upgradelib.php
+++ b/mod/assign/upgradelib.php
@@ -438,78 +438,3 @@ function get_assignments_with_rescaled_null_grades() {
 
     return $assignments;
 }
-
-/**
- * Determined if the assignment has any duplicate group events generated from
- * restoring Course backup without groups, and deletes any records found.
- *
- * Bug fix data clean up for MDL-61870.
- */
-function delete_assignment_duplicate_group_events() {
-    global $DB;
-
-    // Get all Course's assign course modules to check for any duplicate group events to remove.
-    list($coursesinsql, $coursesinparams) = $DB->get_in_or_equal(array_keys(get_courses()), SQL_PARAMS_NAMED);
-
-    $query = "SELECT cm.id AS id,
-                     cm.course AS courseid,
-                     cm.instance AS instanceid
-                FROM {course_modules} cm
-                JOIN {modules} m ON m.id = cm.module
-               WHERE m.name = :modulename
-                 AND (cm.course $coursesinsql)";
-    $params = ['modulename' => 'assign'];
-    $params += $coursesinparams;
-
-    foreach ($DB->get_records_sql($query, $params) as $cm) {
-        $selectgroupevents = "courseid = :courseid
-                              AND modulename = :modulename
-                              AND eventtype = :eventtype
-                              AND instance = :instance
-                              AND groupid <> :groupid
-                              AND priority <> :priority";
-        $paramsgroupevents = [
-            'courseid' => $cm->courseid,
-            'modulename' => 'assign',
-            'eventtype' => 'due',
-            'instance' => $cm->instanceid,
-            'groupid' => 0,
-            'priority' => 0
-        ];
-
-        // Retrieve all the Course's assign events associated with group overrides,
-        // which will be use to look for duplicate records that need to be deleted.
-        foreach ($DB->get_records_select('event', $selectgroupevents, $paramsgroupevents) as $groupevent) {
-            // Delete any duplicates that match the details of the current groupevent but the id does not
-            // match the current groupevent id and course id, groupid is 0, and priority is NULL.
-            $selectduplicates = "id != :eventid
-                                 AND courseid != :courseid
-                                 AND groupid = 0
-                                 AND userid = :userid
-                                 AND repeatid = :repeatid
-                                 AND modulename = :modulename
-                                 AND type = :type
-                                 AND eventtype = :eventtype
-                                 AND timestart = :timestart
-                                 AND timeduration = :timeduration
-                                 AND timesort = :timesort
-                                 AND sequence = :sequence
-                                 AND priority IS NULL";
-            $paramsduplicates = [
-                'eventid' => $groupevent->id,
-                'courseid' => $groupevent->courseid,
-                'groupid' => 0,
-                'userid' => $groupevent->userid,
-                'repeatid' => $groupevent->repeatid,
-                'modulename' => $groupevent->modulename,
-                'type' => $groupevent->type,
-                'eventtype' => $groupevent->eventtype,
-                'timestart' => $groupevent->timestart,
-                'timeduration' => $groupevent->timeduration,
-                'timesort' => $groupevent->timesort,
-                'sequence' => $groupevent->sequence
-            ];
-            $DB->delete_records_select('event', $selectduplicates, $paramsduplicates);
-        }
-    }
-}