diff -u b/core/lib/Drupal/Core/Entity/ContentEntityBase.php b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
--- b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
@@ -897,6 +897,7 @@
     $translation->enforceIsNew = &$this->enforceIsNew;
     $translation->newRevision = &$this->newRevision;
     $translation->entityKeys = &$this->entityKeys;
+    $translation->serializeCompleteEntityStructure = &$this->serializeCompleteEntityStructure;
     $translation->translatableEntityKeys = &$this->translatableEntityKeys;
     $translation->translationInitialize = FALSE;
     $translation->typedData = NULL;
@@ -1173,6 +1174,12 @@
       // original reference with one pointing to a copy of it.
       $enforce_is_new = $this->enforceIsNew;
       $this->enforceIsNew = &$enforce_is_new;
+
+      // Ensure the serializeCompleteEntityStructure property is actually
+      // cloned by overwriting the original reference with one pointing to a
+      // copy of it.
+      $serializeCompleteEntityStructure = $this->serializeCompleteEntityStructure;
+      $this->serializeCompleteEntityStructure = &$serializeCompleteEntityStructure;
     }
   }