Magento 1.9 SUPEE-10415 Causing Product Pages not Found 404 Error: How to Fix

SUPEE-10415 Known issue Issue: Magento 1.9.x displays a “404: Page Not Found” error from the errors/ directory after upgrading to SUPEE-10415. This issue occurs only in Magento installations that run certain third-party extensions. Magento 1.9.3.6 and later with SUPEE-10415 contain a potentially serious bug. Under certain conditions, every product page on your site will get 404 error sometimes. Description: Magento is not properly logging PHP warnings that occur early during page initialization. Instead, of logging the error and continuing operation, Magento generates a 404 page. (Previously, Magento logged these warnings in the system.log file, and execution would continue as usual.)… Read More