🇺🇸United States @Chad Ketchum

I created a patch to resolve the deprecated Request::get() usage and missing session assignment for D11 compatibility.
The 2 issues addressed in the patch are

1. Symfony Request::get() (deprecated scalar handling).
2. Session not set on sub-request (required in Symfony 6 / D11).

This resolved my issue in Drupal 11 PHP 8.3, where only one checkbox per facet could be used until you refreshed the page. The Specific errors were.

• An AJAX HTTP error occurred.
  HTTP Result Code: 500
  Debugging information follows.
  Path: /facets-block-ajax?_wrapper_format=drupal_ajax
  StatusText: Internal Server Error
  ResponseText: The website encountered an unexpected error. Try again later.
  InvalidArgumentException: Expected a scalar value as a 2nd argument to "Symfony\Component\HttpFoundation\InputBag::get()", "array" given. in Symfony\Component\HttpFoundation\InputBag->get() (line 32 of vendor/symfony/http-foundation/InputBag.php).
  Drupal\facets\Controller\FacetBlockAjaxController->ajaxFacetBlockView(Object)
  call_user_func_array(Array, Array) (Line: 123)

• Symfony\Component\HttpKernel\Exception\BadRequestHttpException: Session has not been set.
  in Symfony\Component\HttpKernel\HttpKernel->handle() (line 83 of /vendor/symfony/http-kernel/HttpKernel.php)

• Uncaught Drupal.AjaxError {
  message: "\nAn AJAX HTTP error occurred.\nHTTP Result Code: 500\nDebugging information follows.\nPath: /facets-block-ajax\nStatusText: Internal Server Error\nResponseText: The website encountered an unexpected error. Try again later.InvalidArgumentException: Expected a scalar value as a 2nd argument to \"Symfony\\Component\\HttpFoundation\\InputBag::get()\", \"array\" given. in Symfony\\Component\\HttpFoundation\\InputBag->get() (line 32 of vendor/symfony/http-foundation/InputBag.php).",
  name: "AjaxError",
  stack: "Error at core/misc/ajax.js"
  }

I'm having the same issue. My log Message Symfony\Component\Routing\Exception\RouteNotFoundException: Route "entity.file.edit_form" does not exist. in Drupal\Core\Routing\RouteProvider->getRouteByName() (line 208 of /var/www/html/docroot/core/lib/Drupal/Core/Routing/RouteProvider.php).
Severity Error

Operations
Backtrace
#0 /var/www/html/docroot/core/lib/Drupal/Core/Routing/UrlGenerator.php(443): Drupal\Core\Routing\RouteProvider->getRouteByName()
#1 /var/www/html/docroot/core/lib/Drupal/Core/Routing/UrlGenerator.php(276): Drupal\Core\Routing\UrlGenerator->getRoute()
#2 /var/www/html/docroot/core/lib/Drupal/Core/Render/MetadataBubblingUrlGenerator.php(108): Drupal\Core\Routing\UrlGenerator->generateFromRoute()
#3 /var/www/html/docroot/core/lib/Drupal/Core/Url.php(765): Drupal\Core\Render\MetadataBubblingUrlGenerator->generateFromRoute()
#4 /var/www/html/docroot/core/lib/Drupal/Core/Controller/ControllerBase.php(270): Drupal\Core\Url->toString()
#5 /var/www/html/docroot/modules/contrib/entity_embed/src/Controller/EditEmbeddedEntity.php(22): Drupal\Core\Controller\ControllerBase->redirect()
#6 [internal function]: Drupal\entity_embed\Controller\EditEmbeddedEntity->edit()
#7 /var/www/html/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array()
#8 /var/www/html/docroot/core/lib/Drupal/Core/Render/Renderer.php(638): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#9 /var/www/html/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(121): Drupal\Core\Render\Renderer->executeInRenderContext()
#10 /var/www/html/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext() in my case it happens spacificly when you click the cog Edit the Embedded Entity (Opens in new tab)
#11 /var/www/html/docroot/vendor/symfony/http-kernel/HttpKernel.php(181): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#12 /var/www/html/docroot/vendor/symfony/http-kernel/HttpKernel.php(76): Symfony\Component\HttpKernel\HttpKernel->handleRaw()
#13 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/Session.php(53): Symfony\Component\HttpKernel\HttpKernel->handle()
#14 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle()
#15 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/ContentLength.php(28): Drupal\Core\StackMiddleware\KernelPreHandle->handle()
#16 /var/www/html/docroot/core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\Core\StackMiddleware\ContentLength->handle()
#17 /var/www/html/docroot/core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass()
#18 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\page_cache\StackMiddleware\PageCache->handle()
#19 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()
#20 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/AjaxPageState.php(36): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()
#21 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/StackedHttpKernel.php(51): Drupal\Core\StackMiddleware\AjaxPageState->handle()
#22 /var/www/html/docroot/core/lib/Drupal/Core/DrupalKernel.php(741): Drupal\Core\StackMiddleware\StackedHttpKernel->handle()
#23 /var/www/html/docroot/index.php(19): Drupal\Core\DrupalKernel->handle()
#24 {main}

I'm also having the same issue suddenly in drupal 9.5.10 using version 3.0.2.