I am getting CloudFlare host error page on one of my websites. It comes up randomly. CloudFlare shows me the Host error page(similar to image below) or loads the archived version of page as the Always Online option is enabled in CF.
Details about website and server:
Website Traffic: About 470k a month
Server: $80 per month plan on upCloud
Server config: Ubuntu 20.4 LTS, Apache2, PHP FPM 7.4 and MariaDB
I contacted the upCloud support and they said to check server uptime with
uptime command, and it was up from the time , I created the server. I am also monitoring the website and server PING in Pingdom, no downtime there.
I am using the following Firewall rules in CF for my website.