diff --git a/application/controllers/Backend_api.php b/application/controllers/Backend_api.php
index da14e19c..89f6e43d 100755
--- a/application/controllers/Backend_api.php
+++ b/application/controllers/Backend_api.php
@@ -777,6 +777,7 @@ class Backend_api extends CI_Controller {
                     ->set_output(json_encode(AJAX_SUCCESS));
             }
 
+            $response = AJAX_SUCCESS;
         }
         catch (Exception $exception)
         {
diff --git a/application/models/Appointments_model.php b/application/models/Appointments_model.php
index 539a6e18..bf8d60fe 100644
--- a/application/models/Appointments_model.php
+++ b/application/models/Appointments_model.php
@@ -545,6 +545,7 @@ class Appointments_Model extends CI_Model {
             ->select('count(*) AS attendants_number')
             ->from('appointments')
             ->group_start()
+            ->group_start()
             ->where('start_datetime <=', $slot_start->format('Y-m-d H:i:s'))
             ->where('end_datetime >', $slot_start->format('Y-m-d H:i:s'))
             ->group_end()
@@ -552,6 +553,7 @@ class Appointments_Model extends CI_Model {
             ->where('start_datetime <', $slot_end->format('Y-m-d H:i:s'))
             ->where('end_datetime >=', $slot_end->format('Y-m-d H:i:s'))
             ->group_end()
+            ->group_end()
             ->where('id_services', $service_id)
             ->get()
             ->row()
diff --git a/assets/js/backend_calendar_default_view.js b/assets/js/backend_calendar_default_view.js
index fc46dd3b..698515a5 100755
--- a/assets/js/backend_calendar_default_view.js
+++ b/assets/js/backend_calendar_default_view.js
@@ -270,6 +270,21 @@ window.BackendCalendarDefaultView = window.BackendCalendarDefaultView || {};
         return (result > 500) ? result : 500; // Minimum height is 500px
     }
 
+    /**
+     * Get the event notes for the popup widget.
+     *
+     * @param {Event} event
+     */
+    function getEventNotes(event) {
+        if (!event.data || !event.data.notes) {
+            return '-';
+        }
+
+        var notes = event.data.notes;
+
+        return notes.length > 100 ? notes.substring(0, 100) + '...' : notes;
+    }
+
     /**
      * Calendar Event "Click" Callback
      *
@@ -296,11 +311,6 @@ window.BackendCalendarDefaultView = window.BackendCalendarDefaultView || {};
                 && GlobalVariables.user.privileges.appointments.delete === true)
                 ? 'mr-2' : 'd-none'; // Same value at the time.
 
-            var notes = '';
-            if (event.data) { // Only custom unavailable periods have notes.
-                notes = '<strong>Notes</strong> ' + event.data.notes;
-            }
-
             $html = $('<div/>', {
                 'html': [
                     $('<strong/>', {
@@ -321,8 +331,11 @@ window.BackendCalendarDefaultView = window.BackendCalendarDefaultView || {};
                     }),
                     $('<br/>'),
 
+                    $('<strong/>', {
+                        'text': EALang.notes
+                    }),
                     $('<span/>', {
-                        'text': notes
+                        'text': getEventNotes(event)
                     }),
                     $('<br/>'),
 
@@ -502,6 +515,14 @@ window.BackendCalendarDefaultView = window.BackendCalendarDefaultView || {};
                     }),
                     $('<br/>'),
 
+                    $('<strong/>', {
+                        'text': EALang.notes
+                    }),
+                    $('<span/>', {
+                        'text': getEventNotes(event)
+                    }),
+                    $('<br/>'),
+
                     $('<hr/>'),
 
                     $('<div/>', {
diff --git a/assets/js/backend_calendar_table_view.js b/assets/js/backend_calendar_table_view.js
index c409b9c3..74061040 100755
--- a/assets/js/backend_calendar_table_view.js
+++ b/assets/js/backend_calendar_table_view.js
@@ -997,6 +997,21 @@ window.BackendCalendarTableView = window.BackendCalendarTableView || {};
         }
     }
 
+    /**
+     * Get the event notes for the popup widget.
+     *
+     * @param {Event} event
+     */
+    function getEventNotes(event) {
+        if (!event.data || !event.data.notes) {
+            return '-';
+        }
+
+        var notes = event.data.notes;
+
+        return notes.length > 100 ? notes.substring(0, 100) + '...' : notes;
+    }
+
     /**
      * Calendar Event "Click" Callback
      *
@@ -1023,11 +1038,6 @@ window.BackendCalendarTableView = window.BackendCalendarTableView || {};
                 && GlobalVariables.user.privileges.appointments.delete === true)
                 ? 'mr-2' : 'd-none'; // Same value at the time.
 
-            var notes = '';
-            if (event.data) { // Only custom unavailable periods have notes.
-                notes = '<strong>Notes</strong> ' + event.data.notes;
-            }
-
             $html = $('<div/>', {
                 'html': [
                     $('<strong/>', {
@@ -1046,8 +1056,11 @@ window.BackendCalendarTableView = window.BackendCalendarTableView || {};
                     }),
                     $('<br/>'),
 
+                    $('<strong/>', {
+                        'text': EALang.notes
+                    }),
                     $('<span/>', {
-                        'text': notes
+                        'text': getEventNotes(event)
                     }),
                     $('<br/>'),
 
@@ -1212,6 +1225,14 @@ window.BackendCalendarTableView = window.BackendCalendarTableView || {};
                     }),
                     $('<br/>'),
 
+                    $('<strong/>', {
+                        'text': EALang.notes
+                    }),
+                    $('<span/>', {
+                        'text': getEventNotes(event)
+                    }),
+                    $('<br/>'),
+
                     $('<hr/>'),
 
                     $('<div/>', {
diff --git a/assets/js/backend_calendar_unavailabilities_modal.js b/assets/js/backend_calendar_unavailabilities_modal.js
index 47307b77..353db3a6 100755
--- a/assets/js/backend_calendar_unavailabilities_modal.js
+++ b/assets/js/backend_calendar_unavailabilities_modal.js
@@ -58,7 +58,7 @@ window.BackendCalendarUnavailabilitiesModal = window.BackendCalendarUnavailabili
                 unavailable.id = $dialog.find('#unavailable-id').val();
             }
 
-            var successCallback = function (response) {
+            var successCallback = function () {
                 // Display success message to the user.
                 Backend.displayNotification(EALang.unavailable_saved);
 
@@ -68,15 +68,7 @@ window.BackendCalendarUnavailabilitiesModal = window.BackendCalendarUnavailabili
                 $('#select-filter-item').trigger('change');
             };
 
-            var errorCallback = function (jqXHR, textStatus, errorThrown) {
-                GeneralFunctions.displayMessageBox('Communication Error', 'Unfortunately ' +
-                    'the operation could not complete due to server communication errors.');
-
-                $dialog.find('.modal-message').txt(EALang.service_communication_error);
-                $dialog.find('.modal-message').addClass('alert-danger').removeClass('d-none');
-            };
-
-            BackendCalendarApi.saveUnavailable(unavailable, successCallback, errorCallback);
+            BackendCalendarApi.saveUnavailable(unavailable, successCallback, GeneralFunctions.ajaxFailureHandler);
         });
 
         /**
diff --git a/assets/js/installation.js b/assets/js/installation.js
index 6a677861..ec62dcd2 100644
--- a/assets/js/installation.js
+++ b/assets/js/installation.js
@@ -51,7 +51,7 @@ $(function () {
                 $alert
                     .text('Easy!Appointments has been successfully installed!')
                     .addClass('alert-success')
-                    .show();
+                    .removeClass('hidden');
 
                 setTimeout(function () {
                     window.location.href = GlobalVariables.baseUrl + '/index.php/backend';
@@ -71,7 +71,7 @@ $(function () {
         try {
             $alert
                 .removeClass('alert-danger')
-                .hide();
+                .addClass('hidden');
             $('input').closest('.form-group').removeClass('has-error');
 
             // Check for empty fields.
@@ -116,7 +116,7 @@ $(function () {
             $alert
                 .addClass('alert-danger')
                 .text(error.message)
-                .show();
+                .removeClass('hidden');
 
             return false;
         }