diff --git a/src/addon/mod/lesson/components/index/addon-mod-lesson-index.html b/src/addon/mod/lesson/components/index/addon-mod-lesson-index.html
index e4e86a524..a394f589b 100644
--- a/src/addon/mod/lesson/components/index/addon-mod-lesson-index.html
+++ b/src/addon/mod/lesson/components/index/addon-mod-lesson-index.html
@@ -13,7 +13,7 @@
 <!-- Content. -->
 <core-loading [hideUntil]="loaded" class="core-loading-center">
 
-    <core-tabs [selectedIndex]="selectedTab">
+    <core-tabs [hideUntil]="loaded" [selectedIndex]="selectedTab">
         <!-- Index/Preview tab. -->
         <core-tab [title]="'addon.mod_lesson.preview' | translate">
             <ng-template>
diff --git a/src/addon/mod/lesson/providers/report-link-handler.ts b/src/addon/mod/lesson/providers/report-link-handler.ts
index e07c9978c..76d8703ac 100644
--- a/src/addon/mod/lesson/providers/report-link-handler.ts
+++ b/src/addon/mod/lesson/providers/report-link-handler.ts
@@ -105,7 +105,7 @@ export class AddonModLessonReportLinkHandler extends CoreContentLinksHandlerBase
                 module: module,
                 courseId: Number(courseId),
                 action: 'report',
-                group: groupId
+                group: isNaN(groupId) ? null : groupId
             };
 
             this.linkHelper.goInSite(navCtrl, 'AddonModLessonIndexPage', pageParams, siteId);
diff --git a/src/components/tabs/tabs.ts b/src/components/tabs/tabs.ts
index 2dc4faf73..d17a5e39e 100644
--- a/src/components/tabs/tabs.ts
+++ b/src/components/tabs/tabs.ts
@@ -131,9 +131,7 @@ export class CoreTabsComponent implements OnInit, AfterViewInit, OnChanges, OnDe
     ionViewDidEnter(): void {
         this.isCurrentView = true;
 
-        if (this.initialized) {
-            this.calculateSlides();
-        }
+        this.calculateSlides();
 
         this.registerBackButtonAction();
     }
@@ -188,6 +186,7 @@ export class CoreTabsComponent implements OnInit, AfterViewInit, OnChanges, OnDe
         if (this.getIndex(tab) == -1) {
             this.tabs.push(tab);
             this.sortTabs();
+
             this.calculateSlides();
 
             if (this.initialized && this.tabs.length > 1 && this.tabBarHeight == 0) {
@@ -204,7 +203,7 @@ export class CoreTabsComponent implements OnInit, AfterViewInit, OnChanges, OnDe
      * Calculate slides.
      */
     calculateSlides(): void {
-        if (!this.isCurrentView || !this.tabsShown) {
+        if (!this.isCurrentView || !this.tabsShown || !this.initialized) {
             // Don't calculate if component isn't in current view, the calculations are wrong.
             return;
         }
@@ -288,10 +287,10 @@ export class CoreTabsComponent implements OnInit, AfterViewInit, OnChanges, OnDe
             }
         }
 
+        this.initialized = true;
+
         // Check which arrows should be shown.
         this.calculateSlides();
-
-        this.initialized = true;
     }
 
     /**