--- a/browser/extensions/shield-recipe-client/lib/CleanupManager.jsm
+++ b/browser/extensions/shield-recipe-client/lib/CleanupManager.jsm
@@ -1,21 +1,29 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 this.EXPORTED_SYMBOLS = ["CleanupManager"];
 
-const cleanupHandlers = [];
+const cleanupHandlers = new Set();
 
 this.CleanupManager = {
   addCleanupHandler(handler) {
-    cleanupHandlers.push(handler);
+    cleanupHandlers.add(handler);
+  },
+
+  removeCleanupHandler(handler) {
+    cleanupHandlers.delete(handler);
   },
 
   cleanup() {
     for (const handler of cleanupHandlers) {
-      handler();
+      try {
+        handler();
+      } catch (ex) {
+        Cu.reportError(ex);
+      }
     }
   },
 };

--- a/browser/extensions/shield-recipe-client/lib/Heartbeat.jsm
+++ b/browser/extensions/shield-recipe-client/lib/Heartbeat.jsm
@@ -95,16 +95,17 @@ this.Heartbeat = class {
     this.eventEmitter = eventEmitter;
     this.sandboxManager = sandboxManager;
     this.options = options;
     this.surveyResults = {};
     this.buttons = null;
 
     // so event handlers are consistent
     this.handleWindowClosed = this.handleWindowClosed.bind(this);
+    this.close = this.close.bind(this);
 
     if (this.options.engagementButtonLabel) {
       this.buttons = [{
         label: this.options.engagementButtonLabel,
         callback: () => {
           // Let the consumer know user engaged.
           this.maybeNotifyHeartbeat("Engaged");
 
@@ -203,17 +204,17 @@ this.Heartbeat = class {
 
     const surveyDuration = Preferences.get(PREF_SURVEY_DURATION, 300) * 1000;
     this.surveyEndTimer = setTimeout(() => {
       this.maybeNotifyHeartbeat("SurveyExpired");
       this.close();
     }, surveyDuration);
 
     this.sandboxManager.addHold("heartbeat");
-    CleanupManager.addCleanupHandler(() => this.close());
+    CleanupManager.addCleanupHandler(this.close);
   }
 
   maybeNotifyHeartbeat(name, data = {}) {
     if (this.pingSent) {
       log.warn("Heartbeat event recieved after Telemetry ping sent. name:", name, "data:", data);
       return;
     }
 
@@ -276,20 +277,17 @@ this.Heartbeat = class {
         addClientId: true,
         addEnvironment: true,
       });
 
       // only for testing
       this.eventEmitter.emit("TelemetrySent", Cu.cloneInto(payload, this.sandboxManager.sandbox));
 
       // Survey is complete, clear out the expiry timer & survey configuration
-      if (this.surveyEndTimer) {
-        clearTimeout(this.surveyEndTimer);
-        this.surveyEndTimer = null;
-      }
+      this.endTimerIfPresent("surveyEndTimer");
 
       this.pingSent = true;
       this.surveyResults = null;
     }
 
     if (cleanup) {
       this.cleanup();
     }
@@ -310,37 +308,48 @@ this.Heartbeat = class {
     if (this.options.postAnswerUrl) {
       for (const key in engagementParams) {
         this.options.postAnswerUrl.searchParams.append(key, engagementParams[key]);
       }
       // Open the engagement URL in a new tab.
       this.chromeWindow.gBrowser.selectedTab = this.chromeWindow.gBrowser.addTab(this.options.postAnswerUrl.toString());
     }
 
-    if (this.surveyEndTimer) {
-      clearTimeout(this.surveyEndTimer);
-      this.surveyEndTimer = null;
+    this.endTimerIfPresent("surveyEndTimer");
+
+    this.engagementCloseTimer = setTimeout(() => this.close(), NOTIFICATION_TIME);
+  }
+
+  endTimerIfPresent(timerName) {
+    if (this[timerName]) {
+      clearTimeout(this[timerName]);
+      this[timerName] = null;
     }
-
-    setTimeout(() => this.close(), NOTIFICATION_TIME);
   }
 
   handleWindowClosed() {
     this.maybeNotifyHeartbeat("WindowClosed");
   }
 
   close() {
     this.notificationBox.removeNotification(this.notice);
     this.cleanup();
   }
 
   cleanup() {
+    // Kill the timers which might call things after we've cleaned up:
+    this.endTimerIfPresent("surveyEndTimer");
+    this.endTimerIfPresent("engagementCloseTimer");
+
     this.sandboxManager.removeHold("heartbeat");
     // remove listeners
     this.chromeWindow.removeEventListener("SSWindowClosing", this.handleWindowClosed);
     // remove references for garbage collection
     this.chromeWindow = null;
     this.notificationBox = null;
     this.notification = null;
+    this.notice = null;
     this.eventEmitter = null;
     this.sandboxManager = null;
+    // Ensure we don't re-enter and release the CleanupManager's reference to us:
+    CleanupManager.removeCleanupHandler(this.close);
   }
 };

--- a/browser/extensions/shield-recipe-client/test/browser.ini
+++ b/browser/extensions/shield-recipe-client/test/browser.ini
@@ -1,9 +1,8 @@
 [browser_driver_uuids.js]
 [browser_env_expressions.js]
 [browser_EventEmitter.js]
 [browser_Storage.js]
 [browser_Heartbeat.js]
-skip-if = true # bug 1325409
 [browser_NormandyApi.js]
   support-files =
     test_server.sjs