reverted:
--- b/core/lib/Drupal/Core/Config/Schema/SchemaCheckTrait.php
+++ a/core/lib/Drupal/Core/Config/Schema/SchemaCheckTrait.php
@@ -54,9 +54,8 @@
     }
     $definition = $typed_config->getDefinition($config_name);
     $this->schema = $typed_config->create($definition, $config_data);
-    $errors = array();
     foreach ($config_data as $key => $value) {
+      $errors = $this->checkValue($key, $value);
-      $errors = array_merge($errors, $this->checkValue($key, $value));
     }
     if (empty($errors)) {
       return TRUE;
diff -u b/core/modules/field_ui/src/DisplayOverviewBase.php b/core/modules/field_ui/src/DisplayOverviewBase.php
--- b/core/modules/field_ui/src/DisplayOverviewBase.php
+++ b/core/modules/field_ui/src/DisplayOverviewBase.php
@@ -623,8 +623,12 @@
       case 'update':
         // Store the saved settings, and set the field back to 'non edit' mode.
         $field_name = $trigger['#field_name'];
-        $form_state['plugin_settings'][$field_name]['settings'] = $form_state['values']['fields'][$field_name]['settings_edit_form']['settings'];
-        $form_state['plugin_settings'][$field_name]['third_party_settings'] = $form_state['values']['fields'][$field_name]['settings_edit_form']['third_party_settings'];
+        if (isset($form_state['values']['fields'][$field_name]['settings_edit_form']['settings'])) {
+          $form_state['plugin_settings'][$field_name]['settings'] = $form_state['values']['fields'][$field_name]['settings_edit_form']['settings'];
+        }
+        if (isset($form_state['values']['fields'][$field_name]['settings_edit_form']['third_party_settings'])) {
+          $form_state['plugin_settings'][$field_name]['third_party_settings'] = $form_state['values']['fields'][$field_name]['settings_edit_form']['third_party_settings'];
+        }
         unset($form_state['plugin_settings_edit']);
         break;
 
diff -u b/core/modules/field_ui/src/Tests/ManageDisplayTest.php b/core/modules/field_ui/src/Tests/ManageDisplayTest.php
--- b/core/modules/field_ui/src/Tests/ManageDisplayTest.php
+++ b/core/modules/field_ui/src/Tests/ManageDisplayTest.php
@@ -134,7 +134,7 @@
     $this->assertText('Default empty setting now has a value.');
 
     // Test the settings form behavior. An edit button should be present since
-    // there are thrid party settings to configure.
+    // there are third party settings to configure.
     $edit = array('fields[field_test][type]' => 'field_no_settings', 'refresh_rows' => 'field_test');
     $this->drupalPostAjaxForm(NULL, $edit, array('op' => t('Refresh')));
     $this->assertFieldByName('field_test_settings_edit');