diff --git a/classes/reporter.php b/classes/reporter.php
index 51ebbba..fe1e9df 100644
--- a/classes/reporter.php
+++ b/classes/reporter.php
@@ -136,7 +136,7 @@ public function get_diagnosis() {
      *
      * @return array of diagnosis
      */
-    private function get_diagnosis_data(array $taskids = null) {
+    private function get_diagnosis_data(?array $taskids = null) {
         $diagnoses = array();
         $deletetaskslist = new delete_task_list($this->minimumfaildelay);
         $deletetasks = $deletetaskslist->get_deletetasks();
diff --git a/classes/surgeon.php b/classes/surgeon.php
index 3f18150..89815a9 100644
--- a/classes/surgeon.php
+++ b/classes/surgeon.php
@@ -310,7 +310,13 @@ private function delete_module_cleanly(diagnosis $diagnosis) {
         }
 
         // Notify the competency subsystem.
-        \core_competency\api::hook_course_module_deleted($cm);
+        // The function hook_course_module_deleted() deletes the module context in 5.1+.
+        // context_module::instance($cm->id); causes dml_missing_record_exception when the course_modules record is already absent.
+        try {
+            \core_competency\api::hook_course_module_deleted($cm);
+        } catch (\dml_missing_record_exception $e) {
+            // Context no longer exists; competency data already cleaned up or not present.
+        }
 
         // Delete the context.
         if ($modcontext) {