Any load-balanced infrastructure that uses OpenLiteSpeed as the webserver and has CloudFlare Proxy set-up in front of the load-balancer.
Sporadic 520 Error that do not persist (upon refresh everything seems to work just fine)
No errors in the log that can be correlated/observed
If you have configured the certificates correctly on the load-balanced infrastructure then temporarily suspending the CloudFlare protection for the affected site. This will ensure that the customer experience is not affected any longer.