diff -u b/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php b/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
--- b/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
+++ b/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
@@ -8,11 +8,9 @@
 use Drupal\Core\Ajax\RedirectCommand;
 use Drupal\Core\Ajax\ReplaceCommand;
 use Drupal\Core\Block\BlockPluginInterface;
-use Drupal\Core\Form\DialogFormTrait;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Plugin\PluginWithFormsInterface;
 use Drupal\Core\Url;
-use Drupal\outside_in\OffCanvasFormDialogTrait;
 
 /**
  * Provides form for block instance forms when used in the off-canvas dialog.
@@ -120,26 +118,12 @@
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, FormStateInterface $form_state) {
-    parent::submitForm($form, $form_state);
-    // \Drupal\block\BlockForm::submitForm() always redirects to block listing
-    // via \Drupal\Core\Form\FormStateInterface::setRedirect(). This method
-    // does not work with Ajax submit.
-    $form_state->disableRedirect();
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function buildForm(array $form, FormStateInterface $form_state) {
     $form = parent::buildForm($form, $form_state);
     $form['actions']['submit']['#ajax'] = [
       'callback' => '::submitFormDialog',
-      'event' => 'click',
     ];
-
     $form['#attached']['library'][] = 'core/drupal.dialog.ajax';
-    $form['#attributes']['id'] = 'off-canvas-form';
     return $form;
   }
 
@@ -165,7 +149,7 @@
         '#type' => 'status_messages',
         '#weight' => -1000,
       ];
-      $command = new ReplaceCommand('#off-canvas-form', $form);
+      $command = new ReplaceCommand('[data-drupal-selector="' . $form['#attributes']['data-drupal-selector'] . '"]', $form);
     }
     else {
       if ($redirect_url = $this->getRedirectUrl()) {
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -970,7 +970,7 @@ public function doBuildForm($form_id, &$element, FormStateInterface &$form_state
       // possible to rely on it in JavaScript.
       $element['#attributes']['data-drupal-selector'] = Html::getId($unprocessed_id);
     }
-    else {
+    elseif (!isset($element['#attributes']['data-drupal-selector'])) {
       // Provide a selector usable by JavaScript. As the ID is unique, its not
       // possible to rely on it in JavaScript.
       $element['#attributes']['data-drupal-selector'] = Html::getId($element['#id']);