diff --git a/classes/cron_processor.php b/classes/cron_processor.php
index 59b66ab..31dc36b 100644
--- a/classes/cron_processor.php
+++ b/classes/cron_processor.php
@@ -42,6 +42,12 @@ class cron_processor implements processor {
     /** @var int */
     protected $samplems;
 
+    /** @var bool */
+    protected static $alreadyprofiling = false;
+
+    /** @var bool  */
+    protected $hasoverlapped = false;
+
     /**
      * Initialises the processor
      *
@@ -51,7 +57,10 @@ public function init(manager $manager) {
         $this->sampletime = $manager->get_starttime();
 
         $manager->get_timer()->setCallback(function () use ($manager) {
-            $this->on_interval($manager);
+            if (!$this->hasoverlapped) {
+                // Once overlapping has happened once, we prevent all future partial saving.
+                $this->on_interval($manager);
+            }
         });
 
         // Preload config values to avoid DB access during processing. See manager::get_altconnection() for more information.
@@ -61,7 +70,7 @@ public function init(manager $manager) {
             function () use ($manager) {
                 $manager->get_timer()->stop();
                 $manager->get_profiler()->stop();
-                $this->on_interval($manager);
+                $this->on_interval($manager, true);
                 if ($this->tasksampleset) {
                     $this->process($manager, microtime(true));
                 }
@@ -91,8 +100,22 @@ public function get_min_duration(): float {
      * We then check for a new task with the current sample.
      *
      * @param manager $manager
+     * @param bool $isfinal Set to true when this is called during shutdown.
      */
-    public function on_interval(manager $manager) {
+    public function on_interval(manager $manager, bool $isfinal = false) {
+        // We want to prevent doubling up of processing, so skip if an existing process is still executing.
+        // The profile logs will be kept and processed the next time.
+        if (self::$alreadyprofiling) {
+            $this->hasoverlapped = true;
+            debugging('tool_excimer: starting cron_processor::on_interval when previous call has not yet finished');
+            if ($isfinal) {
+                // This should never happen.
+                debugging('tool_excimer: alreadyprofiling is true during final on_interval.');
+            }
+            return;
+        }
+        self::$alreadyprofiling = true;
+
         $profiler = $manager->get_profiler();
         $log = $profiler->flush();
         $memoryusage = memory_get_usage();  // Record and set initial memory usage at this point.
@@ -135,6 +158,8 @@ public function on_interval(manager $manager) {
             // So it needs to be saved each loop.
             $this->sampletime = $sampletime;
         }
+
+        self::$alreadyprofiling = false;
     }
 
     /**
diff --git a/classes/web_processor.php b/classes/web_processor.php
index 2925f3e..c8b0d28 100644
--- a/classes/web_processor.php
+++ b/classes/web_processor.php
@@ -42,6 +42,10 @@ class web_processor implements processor {
     protected $samplems;
     /** @var bool */
     protected $partialsave;
+    /** @var bool */
+    protected static $alreadyprofiling = false;
+    /** @var bool  */
+    protected $hasoverlapped = false;
 
     /**
      * Construct the web processor.
@@ -78,7 +82,10 @@ public function init(manager $manager) {
 
         if ($this->partialsave) {
             $manager->get_timer()->setCallback(function () use ($manager) {
-                $this->process($manager, false);
+                // Once overlapping has happened once, we prevent all future partial saving.
+                if (!$this->hasoverlapped) {
+                    $this->process($manager, false);
+                }
             });
         }
 
@@ -111,6 +118,19 @@ public function get_min_duration(): float {
      * @throws \dml_exception
      */
     public function process(manager $manager, bool $isfinal) {
+        // We want to prevent overlapping of processing, so skip if an existing process is still executing.
+        // The profile logs will be kept and processed the next time.
+        if (self::$alreadyprofiling) {
+            $this->hasoverlapped = true;
+            debugging('tool_excimer: starting web_processor::process when previous process has not yet finished');
+            if ($isfinal) {
+                // This should never happen.
+                debugging('tool_excimer: alreadyprofiling is true during final process.');
+            }
+            return;
+        }
+        self::$alreadyprofiling = true;
+
         $log = $manager->get_profiler()->flush();
         $this->sampleset->add_many_samples($log);
 
@@ -134,5 +154,7 @@ public function process(manager $manager, bool $isfinal) {
             }
             $this->profile->save_record();
         }
+
+        self::$alreadyprofiling = false;
     }
 }