FIX: On long browsers, you could get a double title

app/assets/javascripts/discourse/components/discourse-topic.js.es6

@@ -37,7 +37,7 @@ export default Ember.Component.extend(AddArchetypeClass, Scrolling, {
     const enteredAt = this.get('enteredAt');
     if (enteredAt && (this.get('lastEnteredAt') !== enteredAt)) {
       this._lastShowTopic = null;
-      this.scrolled();
+      Ember.run.schedule('afterRender', () => this.scrolled());
       this.set('lastEnteredAt', enteredAt);
     }
   },
@@ -131,20 +131,21 @@ export default Ember.Component.extend(AddArchetypeClass, Scrolling, {
       }
     }
 
+
     this.set('hasScrolled', offset > 0);
 
     const topic = this.get('topic');
     const showTopic = this.showTopicInHeader(topic, offset);
     if (showTopic !== this._lastShowTopic) {
-      this._lastShowTopic = showTopic;
-
       if (showTopic) {
         this.appEvents.trigger('header:show-topic', topic);
+        this._lastShowTopic = true;
       } else {
         if (!DiscourseURL.isJumpScheduled()) {
           const loadingNear = topic.get('postStream.loadingNearPost') || 1;
           if (loadingNear === 1) {
             this.appEvents.trigger('header:hide-topic');
+            this._lastShowTopic = false;
           }
         }
       }

app/assets/javascripts/discourse/lib/lock-on.js.es6

@@ -55,6 +55,8 @@ export default class LockOn {
 
     const interval = setInterval(() => {
       let top = this.elementTop();
+      if (top < 0) { top = 0; }
+
       const scrollTop = $(window).scrollTop();
 
       if (typeof(top) === "undefined" || isNaN(top)) {

app/assets/javascripts/discourse/lib/url.js.es6

@@ -108,6 +108,10 @@ const DiscourseURL = Ember.Object.extend({
       }
 
       lockon.lock();
+      if (lockon.elementTop() < 1) {
+        _transitioning = false;
+        return;
+      }
     });
   },