only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Form/FormCache.php
+++ b/core/lib/Drupal/Core/Form/FormCache.php
@@ -4,6 +4,7 @@
 
 use Drupal\Component\Utility\Crypt;
 use Drupal\Core\Access\CsrfTokenGenerator;
+use Drupal\Core\Entity\ContentEntityFormInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\KeyValueStore\KeyValueExpirableFactoryInterface;
 use Drupal\Core\PageCache\RequestPolicyInterface;
@@ -192,9 +193,20 @@ public function setCache($form_build_id, $form, FormStateInterface $form_state)
       $this->keyValueExpirableFactory->get('form')->setWithExpire($form_build_id, $form, $expire);
     }
 
+    // If the form state contains a content entity form object then the entity
+    // should be cached together with the computed field values otherwise when
+    // unserialized the entity might differ from the initial entity used - e.g.
+    // when referenced entities have changed.
+    if (($form_object = $form_state->getFormObject()) && ($form_object instanceof ContentEntityFormInterface)) {
+      $entity = $form_object->getEntity();
+      $entity->serializeComputedFieldValues = TRUE;
+    }
     if ($data = $form_state->getCacheableArray()) {
       $this->keyValueExpirableFactory->get('form_state')->setWithExpire($form_build_id, $data, $expire);
     }
+    if (isset($entity)) {
+      $entity->serializeComputedFieldValues = FALSE;
+    }
   }
 
   /**