468様

プラグイン参照の記述ですが、以下部分のみでした。
\app\proxy\entity\src\Eccube\Entity\Product.php

この時、「Product.php」ファイルを/tmpへ動かしただけでも同じようにServerErrorとなりました。

ログには以下の内容が大量に記載されておりました。
（その他ログは流れてしまい、残っておりませんでした。）

[2021-04-30 06:50:30] front.ERROR [N/A] [476c18e] [N/A] [Eccube\Log\Logger:log:66] - システムエラーが発生しました。 ["Property Eccube\\Entity\\Product::$display_rank does not exist","/var/www/html/vendor/doctrine/persistence/lib/Doctrine/Common/Persistence/Mapping/RuntimeReflectionService.php",63,"#0 /var/www/html/vendor/doctrine/persistence/lib/Doctrine/Common/Persistence/Mapping/RuntimeReflectionService.php(63): ReflectionProperty->__construct('Eccube\\\\Entity\\\\P...', 'display_rank')\n#1 /var/www/html/vendor/doctrine/orm/lib/Doctrine/ORM/Mapping/ClassMetadataInfo.php(964): Doctrine\\Common\\Persistence\\Mapping\\RuntimeReflectionService->getAccessibleProperty('Eccube\\\\Entity\\\\P...', 'display_rank')\n#2 /var/www/html/vendor/doctrine/orm/lib/Doctrine/ORM/Mapping/ClassMetadataFactory.php(750): Doctrine\\ORM\\Mapping\\ClassMetadataInfo->wakeupReflection(Object(Doctrine\\Common\\Persistence\\Mapping\\RuntimeReflectionService))\n#3 /var/www/html/vendor/doctrine/persistence/lib/Doctrine/Common/Persistence/Mapping/AbstractClassMetadataFactory.php(181): Doctrine\\ORM\\Mapping\\ClassMetadataFactory->wakeupReflection(Object(Doctrine\\ORM\\Mapping\\ClassMetadata), Object(Doctrine\\Common\\Persistence\\Mapping\\RuntimeReflectionService))\n#4 /var/www/html/vendor/doctrine/orm/lib/Doctrine/ORM/EntityManager.php(285): Doctrine\\Common\\Persistence\\Mapping\\AbstractClassMetadataFactory->getMetadataFor('Eccube\\\\Entity\\\\P...')\n#5 /var/www/html/var/cache/prod/ContainerNvnxdrx/EntityManager_9a5be93.php(53): Doctrine\\ORM\\EntityManager->getClassMetadata('Eccube\\\\Entity\\\\P...')\n#6 /var/www/html/vendor/doctrine/doctrine-bundle/Repository/ServiceEntityRepository.php(39): EntityManager_9a5be93->getClassMetadata('Eccube\\\\Entity\\\\P...')\n#7 /var/www/html/src/Eccube/Repository/ProductRepository.php(54): Doctrine\\Bundle\\DoctrineBundle\\Repository\\ServiceEntityRepository->__construct(Object(Doctrine\\Bundle\\DoctrineBundle\\Registry), 'Eccube\\\\Entity\\\\P...')\n#8 /var/www/html/var/cache/prod/ContainerNvnxdrx/EccubeProdProjectContainer.php(3030): Eccube\\Repository\\ProductRepository->__construct(Object(Doctrine\\Bundle\\DoctrineBundle\\Registry), Object(Eccube\\Doctrine\\Query\\Queries), Object(Eccube\\Common\\EccubeConfig))\n#9 /var/www/html/var/cache/prod/ContainerNvnxdrx/EccubeProdProjectContainer.php(3094): ContainerNvnxdrx\\EccubeProdProjectContainer->getProductRepositoryService()\n#10 /var/www/html/var/cache/prod/ContainerNvnxdrx/EccubeProdProjectContainer.php(2797): ContainerNvnxdrx\\EccubeProdProjectContainer->getEccubeExtensionService()\n#11 /var/www/html/var/cache/prod/ContainerNvnxdrx/EccubeProdProjectContainer.php(2870): ContainerNvnxdrx\\EccubeProdProjectContainer->getTwigService()\n#12 /var/www/html/var/cache/prod/ContainerNvnxdrx/EccubeProdProjectContainer.php(2423): ContainerNvnxdrx\\EccubeProdProjectContainer->getMobileTemplatePathListenerService()\n#13 /var/www/html/vendor/symfony/event-dispatcher/EventDispatcher.php(231): ContainerNvnxdrx\\EccubeProdProjectContainer->ContainerNvnxdrx\\{closure}()\n#14 /var/www/html/vendor/symfony/event-dispatcher/EventDispatcher.php(61): Symfony\\Component\\EventDispatcher\\EventDispatcher->sortListeners('kernel.request')\n#15 /var/www/html/vendor/symfony/event-dispatcher/ContainerAwareEventDispatcher.php(129): Symfony\\Component\\EventDispatcher\\EventDispatcher->getListeners('kernel.request')\n#16 /var/www/html/vendor/symfony/event-dispatcher/EventDispatcher.php(43): Symfony\\Component\\EventDispatcher\\ContainerAwareEventDispatcher->getListeners('kernel.request')\n#17 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(127): Symfony\\Component\\EventDispatcher\\EventDispatcher->dispatch('kernel.request', Object(Symfony\\Component\\HttpKernel\\Event\\GetResponseEvent))\n#18 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\\Component\\HttpKernel\\HttpKernel->handleRaw(Object(Symfony\\Component\\HttpFoundation\\Request), 1)\n#19 /var/www/html/vendor/symfony/http-kernel/Kernel.php(200): Symfony\\Component\\HttpKernel\\HttpKernel->handle(Object(Symfony\\Component\\HttpFoundation\\Request), 1, true)\n#20 /var/www/html/index.php(76): Symfony\\Component\\HttpKernel\\Kernel->handle(Object(Symfony\\Component\\HttpFoundation\\Request))\n#21 {main}"] [, , , , ]