diff -uNr ./moodle_orig/mod/quiz/editrandom.php ./moodle/mod/quiz/editrandom.php
--- ./moodle_orig/mod/quiz/editrandom.php	2020-03-09 19:29:59.000000000 +0100
+++ ./moodle/mod/quiz/editrandom.php	2020-05-18 01:20:38.000000000 +0200
@@ -149,7 +149,7 @@
     // Now, delete the remaining records.
     if (!empty($recordstokeep)) {
         list($select, $params) = $DB->get_in_or_equal($recordstokeep, SQL_PARAMS_QM, 'param', false);
-        $DB->delete_records_select('quiz_slot_tags', "id $select", $params);
+        $DB->delete_records_select('quiz_slot_tags', "slotid = {$slot->id} AND id $select", $params);
     } else {
         $DB->delete_records('quiz_slot_tags', array('slotid' => $slot->id));
     }
diff -uNr ./moodle_orig/mod/quiz/locallib.php ./moodle/mod/quiz/locallib.php
--- ./moodle_orig/mod/quiz/locallib.php	2020-03-09 19:29:59.000000000 +0100
+++ ./moodle/mod/quiz/locallib.php	2020-05-18 01:21:56.000000000 +0200
@@ -2524,7 +2524,7 @@
                 }
             }
 
-            $carry[$slottag->slotid][] = $slottag;
+            $carry[$slottag->slotid][$slottag->id] = $slottag;
             return $carry;
         },
         $emptytagids