Thanks for getting back! Sorry! I forgot, the site I'm having issues with I will link below - I have two licenses across two websites. I do apologise if there's any issues accessing the website as I did have country blocking in place. I have removed the blocks to help you guys access the site so hopefully you won't have any problems.
I don't currently have CloudFlare linked to any websites and haven't done for over 12 months. I just logged in there to be sure and nothing active or linked to any websites.
I have cleared WP-Rocket's Cache (pretty much where I started) and no luck. To be honest, I don't know how to check if the minified JS and CSS were regenerated after the update - never had to do that before. However, I did disable JS and CSS minification and ran a test after clearing the cache again and it made no difference. I also deactivated the WP-Rocket plug-in entirely incase it was causing issue and made no difference.
The issue is appearing on actual devices as well as the XTheme "Customise" device preview so I will attempt to attach screenshots from the Customise screen. Each page loads with the base menu in full view. Even when clicking/touching the menu symbol it does not collapse.