diff --git a/mod/h5pactivity/db/upgrade.php b/mod/h5pactivity/db/upgrade.php
index 449a9b48997..5f740909677 100644
--- a/mod/h5pactivity/db/upgrade.php
+++ b/mod/h5pactivity/db/upgrade.php
@@ -252,5 +252,20 @@ function xmldb_h5pactivity_upgrade($oldversion) {
     // Automatically generated Moodle v4.2.0 release upgrade line.
     // Put any upgrade step following this.
 
+    if ($oldversion < 2023042401) {
+
+        // Remove any orphaned attempt/result records (pointing to non-existing activities).
+        $DB->delete_records_select('h5pactivity_attempts', 'NOT EXISTS (
+            SELECT 1 FROM {h5pactivity} h5p WHERE h5p.id = {h5pactivity_attempts}.h5pactivityid
+        )');
+
+        $DB->delete_records_select('h5pactivity_attempts_results', 'NOT EXISTS (
+            SELECT 1 FROM {h5pactivity_attempts} attempt WHERE attempt.id = {h5pactivity_attempts_results}.attemptid
+        )');
+
+        // H5pactivity savepoint reached.
+        upgrade_mod_savepoint(true, 2023042401, 'h5pactivity');
+    }
+
     return true;
 }
diff --git a/mod/h5pactivity/lib.php b/mod/h5pactivity/lib.php
index 114abcdbf6b..5ab26d7f1f0 100644
--- a/mod/h5pactivity/lib.php
+++ b/mod/h5pactivity/lib.php
@@ -152,6 +152,13 @@ function h5pactivity_delete_instance(int $id): bool {
         $xapihandler->wipe_states($context->id);
     }
 
+    // Remove activity record, and all associated attempt data.
+    $attemptids = $DB->get_fieldset_select('h5pactivity_attempts', 'id', 'h5pactivityid = ?', [$id]);
+    if ($attemptids) {
+        $DB->delete_records_list('h5pactivity_attempts_results', 'attemptid', $attemptids);
+        $DB->delete_records_list('h5pactivity_attempts', 'id', $attemptids);
+    }
+
     $DB->delete_records('h5pactivity', ['id' => $id]);
 
     h5pactivity_grade_item_delete($activity);
diff --git a/mod/h5pactivity/version.php b/mod/h5pactivity/version.php
index 88ab8480a61..5993c8adecd 100644
--- a/mod/h5pactivity/version.php
+++ b/mod/h5pactivity/version.php
@@ -25,5 +25,5 @@
 defined('MOODLE_INTERNAL') || die();
 
 $plugin->component = 'mod_h5pactivity';
-$plugin->version = 2023042400;
+$plugin->version = 2023042401;
 $plugin->requires = 2023041800;