diff --git a/ui/src/app/extension/extension-table.directive.js b/ui/src/app/extension/extension-table.directive.js
index 5e5b036a13..24e98420f1 100644
--- a/ui/src/app/extension/extension-table.directive.js
+++ b/ui/src/app/extension/extension-table.directive.js
@@ -77,6 +77,7 @@ function ExtensionTableController($scope, $filter, $document, $translate, types,
         if (newVal) {
             if ($scope.subscriber) {
                 telemetryWebsocketService.unsubscribe($scope.subscriber);
+                $scope.subscriber = null;
             }
 
             vm.subscribed = false;
@@ -88,6 +89,13 @@ function ExtensionTableController($scope, $filter, $document, $translate, types,
         }
     });
 
+    $scope.$on('$destroy', function() {
+        if ($scope.subscriber) {
+            telemetryWebsocketService.unsubscribe($scope.subscriber);
+            $scope.subscriber = null;
+        }
+    });
+
     $scope.$watch("vm.query.search", function(newVal, prevVal) {
         if (!angular.equals(newVal, prevVal) && vm.query.search != null) {
             updateExtensions();
@@ -325,9 +333,8 @@ function ExtensionTableController($scope, $filter, $document, $translate, types,
                         vm.subscribed = true;
                     }
                 };
+                telemetryWebsocketService.subscribe($scope.subscriber);
             }
-            telemetryWebsocketService.subscribe($scope.subscriber);
-
         }
     }
     function onSubscriptionData(data) {
diff --git a/ui/src/app/extension/extensions-forms/extension-form-opc.tpl.html b/ui/src/app/extension/extensions-forms/extension-form-opc.tpl.html
index 01b4f86355..304247cff7 100644
--- a/ui/src/app/extension/extensions-forms/extension-form-opc.tpl.html
+++ b/ui/src/app/extension/extensions-forms/extension-form-opc.tpl.html
@@ -95,10 +95,10 @@
                                                     >extension.field-required</div>
                                                     <div translate
                                                          ng-message="min"
-                                                    >Port should be in a range from 1 to 65535</div>
+                                                    >extension.port-range</div>
                                                     <div translate
                                                          ng-message="max"
-                                                    >Port should be in a range from 1 to 65535</div>
+                                                    >extension.port-range</div>
                                                 </div>
                                             </md-input-container>
                                         </div>