OpenCart 3 Core Session, Cart Sync & Checkout Payment Method Bug Fix

We run an OpenCart store (hosted on a cPanel VPS) and urgently need a verified OpenCart specialist to fix a critical session/checkout breakdown and optimize our store images today. The Context: A full-page caching extension (Lightning) was uninstalled... (Budget: $30 - $250 USD, Jobs: AJAX, Apache, cPanel, Linux, MySQL, Open Cart, PHP, Web Development)