Failed to receive status information from Apache error

Hello i updated my cpanel to latest version (78.0.21) a few hours ago but since 30 minutes ago Apache got down. When i try to browse my websites, i am getting error 521 and also i get this error on WHM: Failed to receive status information from Apache. Unable to connect to local httpd server. exactly after 30 minutes web server backed to normal and websites are working fine now but i wonder why does this happen regularly? How can i stop this 30 minutes down times?