I tested https://www.chewy.com/ on a clean install of FireFox ESR with no plugins and the site works fine.
Try purging Firefox and reinstalling. sudo apt purge firefox-esr sudo apt install firefox-esr Google Chrome also works fine with no issues as well. -- ⢀⣴⠾⠻⢶⣦⠀ ⣾⠁⢠⠒⠀⣿⡁ Debian - The universal operating system ⢿⡄⠘⠷⠚⠋⠀ https://www.debian.org/ ⠈⠳⣄⠀⠀
