May I ask if that’s your website which you do manage, or?
After you disabled “I am under an attack mode” → I’d suggest you to rather use Page Rules and for specific webpages like “chechout” to choose Security Level and set it to “High”, have you tried to clear the cache at Cloudflare by navigating to the Caching → Configuration and clicking on the button “Purge Everything”?
May I ask have you tried using a different Web browser, or tried clearing your Web browser cache?
How about using a Private window (Incognito mode) or a VPN connection if possible?
Is it the same behaviour on your mobile phone (4G LTE, mobile data, cellular)?
Do you use any particular anti-virus software or some kind of an Web browser extension?
