ERPNext drops sometimes and suddenly it goes up

[dirkvdl16]

The default fail2ban rules are quite strict. Multiple client errors (404’s or disconnects) may actually trigger a temporary ban. The best is to whitelist the public IP from where you want to access your ERPnext instance:

Instance refuses IP address at intervals

I had faced the same issue. Solved by adding my IP address to fail2ban’s whitelist referring below article. https://blog.rimuhosting.com/2017/02/24/whitelist-your-own-computer-in-fail2ban/