Site Homepage redirecting to 404 page

My site homepage redirects to a 404 page...

The weird thing is, it doesn't always happen. Sometimes on desktop, always on mobile.
When it does happen, it adds the following to the URL: mysite.com/____proof-of-work/validate/56134/...

This is the only page that is having this issue.

I've already reset the permalinks and checked the htaccess file.

Any other fixes?

p.s. I use Cloudflare

First create a backup, Then You can remove the url permanently, after that create new page and restore the that page again.
Also, if you are using wp, try to disabled recent installed plugin , Then check your website using few different browser.