503 service unavailable error after login twice

Hi everyone,

I face currently a strange issue and I have no clue why this happens.
I have installed a Sylius Standard edition (v1.10.14 and PHP 8.1) with some product categories, product options, product attributes and few products. If I login the first time into the Admin view it works. If I logout again and try to login again for a second time I receive a 503 Service unavailable error. If I clear the cache by manually removing the var/cache/prod folder the login works again, but after trying to login a second time it again throws a 503 service unavailable error. In the var/log I don’t receive any appropriate error log.

On my local machine the same installation works fine without any problems.

I assume there is some misconfiguration on my Shared hosting server in combination with the Caching. Everytime I clear the cache it works for one request or so and then the second login fails. The Frontend Shop works, also if I receive the 503 error in the Admin backend.

Do you still have any idea or any hints to resolve the issue or what the cause is?

Thanks for any hints and help!

After some research I have found the following thread in Stackoverflow: https://stackoverflow.com/questions/73372479/very-strange-behavior-error-503-with-php-fpm-mariadb-and-symfony-form-doctrin

We had the same issue mentioned in the Stackoverflow thread. Our Hosting provider has a PHP 8.1 installation with this ionCube module which produced this 503 service unavailable. If I have switched to the PHP 8.0 version which did not have this ionCube module and it worked.

So there seems to be an issue with Sylius/Symfony and Admin UI or Cache in combination with this ionCube module.

Does anybody know this issue or has other experiences with this ionCube module?