diff --git a/app/assets/javascripts/discourse/app/controllers/exception.js b/app/assets/javascripts/discourse/app/controllers/exception.js
index d4a285b1f14..628f4921f09 100644
--- a/app/assets/javascripts/discourse/app/controllers/exception.js
+++ b/app/assets/javascripts/discourse/app/controllers/exception.js
@@ -1,5 +1,6 @@
 import { alias, equal, gte, none } from "@ember/object/computed";
 import discourseComputed, { on } from "discourse-common/utils/decorators";
+import DiscourseURL from "discourse/lib/url";
 import Controller from "@ember/controller";
 import I18n from "I18n";
 import { schedule } from "@ember/runloop";
@@ -31,15 +32,15 @@ export default Controller.extend({
   thrown: null,
   lastTransition: null,
 
-  @discourseComputed
-  isNetwork() {
+  @discourseComputed("thrown")
+  isNetwork(thrown) {
     // never made it on the wire
-    if (this.get("thrown.readyState") === 0) {
+    if (thrown && thrown.readyState === 0) {
       return true;
     }
 
     // timed out
-    if (this.get("thrown.jqTextStatus") === "timeout") {
+    if (thrown && thrown.jqTextStatus === "timeout") {
       return true;
     }
 
@@ -65,16 +66,18 @@ export default Controller.extend({
     this.set("loading", false);
   },
 
-  @discourseComputed("isNetwork", "isServer", "isUnknown")
-  reason() {
-    if (this.isNetwork) {
+  @discourseComputed("isNetwork", "thrown.status", "thrown")
+  reason(isNetwork, thrownStatus, thrown) {
+    if (isNetwork) {
       return I18n.t("errors.reasons.network");
-    } else if (this.isServer) {
+    } else if (thrownStatus >= 500) {
       return I18n.t("errors.reasons.server");
-    } else if (this.isNotFound) {
+    } else if (thrownStatus === 404) {
       return I18n.t("errors.reasons.not_found");
-    } else if (this.isForbidden) {
+    } else if (thrownStatus === 403) {
       return I18n.t("errors.reasons.forbidden");
+    } else if (thrown === null) {
+      return I18n.t("errors.reasons.unknown");
     } else {
       // TODO
       return I18n.t("errors.reasons.unknown");
@@ -83,30 +86,42 @@ export default Controller.extend({
 
   requestUrl: alias("thrown.requestedUrl"),
 
-  @discourseComputed("networkFixed", "isNetwork", "isServer", "isUnknown")
-  desc() {
-    if (this.networkFixed) {
+  @discourseComputed(
+    "networkFixed",
+    "isNetwork",
+    "thrown.status",
+    "thrown.statusText",
+    "thrown"
+  )
+  desc(networkFixed, isNetwork, thrownStatus, thrownStatusText, thrown) {
+    if (networkFixed) {
       return I18n.t("errors.desc.network_fixed");
-    } else if (this.isNetwork) {
+    } else if (isNetwork) {
       return I18n.t("errors.desc.network");
-    } else if (this.isNotFound) {
+    } else if (thrownStatus === 404) {
       return I18n.t("errors.desc.not_found");
-    } else if (this.isServer) {
+    } else if (thrownStatus === 403) {
+      return I18n.t("errors.desc.forbidden");
+    } else if (thrownStatus >= 500) {
       return I18n.t("errors.desc.server", {
-        status: this.get("thrown.status") + " " + this.get("thrown.statusText"),
+        status: thrownStatus + " " + thrownStatusText,
       });
+    } else if (thrown === null) {
+      return I18n.t("errors.desc.unknown");
     } else {
       // TODO
       return I18n.t("errors.desc.unknown");
     }
   },
 
-  @discourseComputed("networkFixed", "isNetwork", "isServer", "isUnknown")
-  enabledButtons() {
-    if (this.networkFixed) {
+  @discourseComputed("networkFixed", "isNetwork", "lastTransition")
+  enabledButtons(networkFixed, isNetwork, lastTransition) {
+    if (networkFixed) {
       return [ButtonLoadPage];
-    } else if (this.isNetwork) {
+    } else if (isNetwork) {
       return [ButtonBackDim, ButtonTryAgain];
+    } else if (!lastTransition) {
+      return [ButtonBackBright];
     } else {
       return [ButtonBackBright, ButtonTryAgain];
     }
@@ -114,14 +129,25 @@ export default Controller.extend({
 
   actions: {
     back() {
-      window.history.back();
+      // Strip off subfolder
+      const currentURL = DiscourseURL.router.location.getURL();
+      if (this.lastTransition && currentURL !== "/exception") {
+        this.lastTransition.abort();
+        this.setProperties({ lastTransition: null, thrown: null });
+        // Can't use routeTo because it handles navigation to the same page
+        DiscourseURL.handleURL(currentURL);
+      } else {
+        window.history.back();
+      }
     },
 
     tryLoading() {
       this.set("loading", true);
 
       schedule("afterRender", () => {
-        this.lastTransition.retry();
+        const transition = this.lastTransition;
+        this.setProperties({ lastTransition: null, thrown: null });
+        transition.retry();
         this.set("loading", false);
       });
     },
diff --git a/app/assets/javascripts/discourse/app/lib/url.js b/app/assets/javascripts/discourse/app/lib/url.js
index c412b6b3912..441d6b8d1c7 100644
--- a/app/assets/javascripts/discourse/app/lib/url.js
+++ b/app/assets/javascripts/discourse/app/lib/url.js
@@ -483,6 +483,7 @@ const DiscourseURL = EmberObject.extend({
 
     transition._discourse_intercepted = true;
     transition._discourse_anchor = elementId;
+    transition._discourse_original_url = path;
 
     const promise = transition.promise || transition;
     promise.then(() => jumpToElement(elementId));
diff --git a/app/assets/javascripts/discourse/app/routes/application.js b/app/assets/javascripts/discourse/app/routes/application.js
index dc2f2650826..9099ffffb38 100644
--- a/app/assets/javascripts/discourse/app/routes/application.js
+++ b/app/assets/javascripts/discourse/app/routes/application.js
@@ -94,13 +94,7 @@ const ApplicationRoute = DiscourseRoute.extend(OpenComposer, {
     },
 
     error(err, transition) {
-      let xhr = {};
-      if (err.jqXHR) {
-        xhr = err.jqXHR;
-      }
-
-      const xhrOrErr = err.jqXHR ? xhr : err;
-
+      const xhrOrErr = err.jqXHR ? err.jqXHR : err;
       const exceptionController = this.controllerFor("exception");
 
       const c = window.console;
diff --git a/app/assets/javascripts/discourse/app/templates/exception.hbs b/app/assets/javascripts/discourse/app/templates/exception.hbs
index 41555d71012..7e3ef7252b8 100644
--- a/app/assets/javascripts/discourse/app/templates/exception.hbs
+++ b/app/assets/javascripts/discourse/app/templates/exception.hbs
@@ -5,9 +5,11 @@
     <div class="error-page">
       <div class="face">:(</div>
       <div class="reason">{{reason}}</div>
-      <div class="url">
-        {{i18n "errors.prev_page"}} <a href={{requestUrl}} data-auto-route="true">{{requestUrl}}</a>
-      </div>
+      {{#if requestUrl}}
+        <div class="url">
+          {{i18n "errors.prev_page"}} <a href={{requestUrl}} data-auto-route="true">{{requestUrl}}</a>
+        </div>
+      {{/if}}
       <div class="desc">
         {{#if networkFixed}}
           {{d-icon "check-circle"}}
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index e7fcbdcd25b..ca9796b9621 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -299,7 +299,7 @@ class ApplicationController < ActionController::Base
       with_resolved_locale(check_current_user: false) do
         # Include error in HTML format for topics#show.
         if (request.params[:controller] == 'topics' && request.params[:action] == 'show') || (request.params[:controller] == 'categories' && request.params[:action] == 'find_by_slug')
-          opts[:extras] = { html: build_not_found_page(error_page_opts) }
+          opts[:extras] = { html: build_not_found_page(error_page_opts), group: error_page_opts[:group] }
         end
       end