Breaks media_entity + entity_embed widget

When using this module in combination with entity_embed it completely breaks the widget. When clicking the media selection the AJAX does not run and the console logs:

Statustext: 500 Service unavailable (with message)
Antworttext: Auf der Website ist ein unvorhergesehener Fehler aufgetreten. Bitte versuchen Sie es später nochmal.LogicException: The database connection is not serializable. This probably means you are serializing an object that has an indirect reference to the database connection. Adjust your code so that is not necessary. Alternatively, look at DependencySerializationTrait as a temporary solution. in Drupal\Core\Database\Connection->__sleep() (line 1472 of core/lib/Drupal/Core/Database/Connection.php). serialize(Array) (Line: 14)
Drupal\Component\Serialization\PhpSerialize::encode(Array) (Line: 81)
Drupal\Core\KeyValueStore\DatabaseStorageExpirable->setWithExpire('form-JtyNbWCOv5i9ZL-UOUXltp5-zDkZc1KaAcUilBJWIVc', Array, 21600) (Line: 197)
Drupal\Core\Form\FormCache->setCache('form-JtyNbWCOv5i9ZL-UOUXltp5-zDkZc1KaAcUilBJWIVc', Array, Object) (Line: 441)
Drupal\Core\Form\FormBuilder->setCache('form-JtyNbWCOv5i9ZL-UOUXltp5-zDkZc1KaAcUilBJWIVc', Array, Object) (Line: 419)
Drupal\Core\Form\FormBuilder->rebuildForm('node_page_edit_form', Object, Array) (Line: 621)
Drupal\Core\Form\FormBuilder->processForm('node_page_edit_form', Array, Object) (Line: 314)
Drupal\Core\Form\FormBuilder->buildForm('node_page_edit_form', Object) (Line: 74)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 576)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
call_user_func_array(Object, Array) (Line: 153)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 68)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 50)
Drupal\ban\BanMiddleware->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 50)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 657)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)
ajax.js:110:32

I think the reason may be related to: #2893029: EntityType objects cannot be reliably serialized without DependencySerializationTrait
I tried the patch from #2893029: EntityType objects cannot be reliably serialized without DependencySerializationTrait but it does not solve the problem with background_image. After uninstalling background_image without any other changes everything works fine.

background_image uses StringTranslationTrait in:

• src/BackgroundImageManager.php:use Drupal\Core\StringTranslation\StringTranslationTrait;
• src/BackgroundImageManager.php: use StringTranslationTrait;
• src/Entity/BackgroundImage.php:use Drupal\Core\StringTranslation\StringTranslationTrait;
• src/Entity/BackgroundImage.php: use StringTranslationTrait;
• src/Form/BackgroundImageForm.php:use Drupal\Core\StringTranslation\StringTranslationTrait;
• src/Form/BackgroundImageForm.php: use StringTranslationTrait;