Worked on stabilizing core storefront subsystems in the opencart/opencart repository, focusing on backend development using PHP. Addressed reliability issues in class loading by fixing the autoloader within the storeInstance, which reduced runtime errors and improved the consistency of catalog operations. Enhanced the subscription processing workflow by initializing shipping address information and adding safeguards for missing shipping methods in the subscription cron controller, leading to smoother order processing. These targeted bug fixes contributed to a more resilient checkout and subscription experience, emphasizing robust error handling and system reliability within the existing codebase, without introducing new features during the development period.