Angular 7: Website runs fine on Chrome/Edge/Brave but not Safari/Firefox

I have an angular 7 website (https://quizmenot.com) that runs fine on Chrome/Edge/Brave browsers, but not Firefox or Safari. The issue I believe is causing this is an error with Zone.js. Here is a screenshot of the error on Firefox: https://imgur.com/a/7izYXTB

This error reads: "Uncaught Error: Zone.js has detected that ZoneAwarePromise `(window|global).Promise` has been overwritten. Most likely cause is that a Promise polyfill has been loaded after Zone.js (Polyfilling Promise api is not necessary when zone.js is loaded. If you must load one, do so before loading zone.js.)."

I followed this StackOverflow thread (https://stackoverflow.com/questions/42741628/unhandled-promise-rejection-zone-js-has-detected-that-zoneawarepromise-window), which suggests I move the zone.js import from polyfills.ts to main.ts, which helped get the site running on Firefox on my localhost:4200, but not on the live site (https://quizmenot.com). I also tried installing the latest zone.js with `npm install zone.js@latest --save` and `npm install zone.js@0.10.3`, but neither worked.

Please help me get the website running on Safari and Firefox.