Getting email reports of 521 "Server Unreachable" when using Cloudflare Cache and Cloudflare Pages

I have setup my GitHub repository to push my website to Cloudflare pages. I have also setup Cloudflare cache on the website served from Cloudflare pages. I am getting reports of 521 “Server Unreachable” by email. Any suggestion on how to troubleshoot this? Everything was working fine for a couple of months and only started seeing the errors over the last few days. I have not pushed any changes in the past couple of weeks from Github.

Also, not seeing any issues when I browse the website.

Created ticket 2762652.

Can you please reply there with the requested information?