Seeing 520 Errors Randomly - Can't Track Down

Hello, we run a website using Cloudflare Pro on the front end, which talks to GCP load balancer - and we are having a heck of a time diagnosing 520 error’s we’re seeing in client’s JS logs and in Cloudflare’s own “traffic” reports. We have full logging turned on in GCP’s load balancer, so we can see every web request being made/etc - and we don’t see anything coming in around the time that these errors are happening. So it’s like the requests aren’t even making it to GCP’s load balancer. We’re totally stumped on how to track this down further. We can’t really easily turn off Cloudflare since it’s providing our SSL certs/etc for us.

Before we open a ticket with Cloudflare to research further, does anyone have any guidance on tracking down occasional 520s?

We’re also seeing 502’s occasionally, but I believe that to be a separate issue…