Created an account just to chime in on this issue a lot of people have been having. We have been following this as our site is impacted as well. We have a solid infrastructure setup and nothing is showing in the logs on our end. This is causing issues with sales, interrupting staff work, and syncing with external service providers. We have turned off cloudflare for now.
I totally understand that often 520 is caused by site errors, but I wish CF would take all these complaints more seriously. They posted it is “fixed” but clearly it isn’t. Very frustrating.