Error after upgrading 3.0.3.8 to 3.0.3.9

Iv'e done an upgrade from OC 3.0.3.8 to OC 3.0.3.9. I uploaded the 3.0.3.9 content to overwrite the existing version (except for config and index files). The origin storage folder is replaced with the new content from system/storage. It works fine when I use PHP 7.4 but when changing to PHP 8 I get the error below and the admin part stops working. I would appreciate som hint how to solve the issue.

Uncaught TypeError: Unsupported operand types: string + string in system/storage/cache/template/9b/9b224237cd5aea68844674c9fdd04428.php:1895
Stack trace:
#0 system/storage/vendor/twig/twig/src/Template.php(394): __TwigTemplate_03c0cd529c4b010021cee278f0a65a63->doDisplay()
#1 system/storage/vendor/twig/twig/src/Template.php(367): Twig\Template->displayWithErrorHandling()
#2 system/storage/vendor/twig/twig/src/Template.php(379): Twig\Template->display()
#3 system/storage/vendor/twig/twig/src/TemplateWrapper.php(38): Twig\Template->render()
#4 system/storage/vendor/twig/twig/src/Environment.php(280): Twig\TemplateWrapper->render()
#5 vqmod/vqcache/vq2-system_storage_modification_system_library_template_twig.php(61): Twig\Environment->render()
#6 system/storage/modification/system/library/template.php(59): Template\Twig->render()
#7 vqmod/vqcache/vq2-system_storage_modification_system_engine_loader.php(139): Template->render()
#8 vqmod/vqcache/vq2-system_storage_modification_catalog_controller_product_product.php(996): Loader->view()
#9 catalog/controller/extension/lightning/beta.php(266): ControllerProductProduct->index()
#10 vqmod/vqcache/vq2-system_storage_modification_system_engine_action.php(63): Wkn()
#11 system/storage/modification/catalog/controller/startup/router.php(29): Action->execute()
#12 catalog/controller/extension/lightning/beta.php(266): ControllerStartupRouter->index()
#13 vqmod/vqcache/vq2-system_storage_modification_system_engine_action.php(63): Wkn()
#14 vqmod/vqcache/vq2-system_storage_modification_system_engine_router.php(138): Action->execute()
#15 vqmod/vqcache/vq2-system_storage_modification_system_engine_router.php(123): Router->execute()
#16 system/framework.php(179): Router->dispatch()
#17 vqmod/vqcache/vq2-system_startup.php(104): require_once('/home/torshamma...')
#18 index.php(27): start()
#19 {main}

Next Twig\Error\RuntimeError: An exception has been thrown during the rendering of a template ("Unsupported operand types: string + string") in "journal3/template/product/product.twig" at line 572. in system/storage/vendor/twig/twig/src/Template.php:408
Stack trace:
#0 system/storage/vendor/twig/twig/src/Template.php(367): Twig\Template->displayWithErrorHandling()
#1 system/storage/vendor/twig/twig/src/Template.php(379): Twig\Template->display()
#2 system/storage/vendor/twig/twig/src/TemplateWrapper.php(38): Twig\Template->render()
#3 system/storage/vendor/twig/twig/src/Environment.php(280): Twig\TemplateWrapper->render()
#4 vqmod/vqcache/vq2-system_storage_modification_system_library_template_twig.php(61): Twig\Environment->render()
#5 system/storage/modification/system/library/template.php(59): Template\Twig->render()
#6 vqmod/vqcache/vq2-system_storage_modification_system_engine_loader.php(139): Template->render()
#7 vqmod/vqcache/vq2-system_storage_modification_catalog_controller_product_product.php(996): Loader->view()
#8 catalog/controller/extension/lightning/beta.php(266): ControllerProductProduct->index()
#9 vqmod/vqcache/vq2-system_storage_modification_system_engine_action.php(63): Wkn()
#10 system/storage/modification/catalog/controller/startup/router.php(29): Action->execute()
#11 catalog/controller/extension/lightning/beta.php(266): ControllerStartupRouter->index()
#12 vqmod/vqcache/vq2-system_storage_modification_system_engine_action.php(63): Wkn()
#13 vqmod/vqcache/vq2-system_storage_modification_system_engine_router.php(138): Action->execute()
#14 vqmod/vqcache/vq2-system_storage_modification_system_engine_router.php(123): Router->execute()
#15 system/framework.php(179): Router->dispatch()
#16 vqmod/vqcache/vq2-system_startup.php(104): require_once('/home/torshamma...')
#17 index.php(27): start()
#18 {main}
thrown in system/storage/vendor/twig/twig/src/Template.php:408

Get in touch with the Journal3 support, this is not an OpenCart issue. In the standard OC 3.0.3.9 framework, the Twig rendering engine works just fine for PHP 8 versions.

Thank you for your answer.