If you use Apache2 / Apache24 and anti-hammering tools like the Modul evasive and security2 as addon fail2ban than you can fail blogging.
Problems:
- Apache2 Module “evasive” must be fine tuned for WordPress go /etc/apache2/
- if you use default enabled auto-safe drafts of posts can let you look like a Attacker so disable auto save by wp-config set “define(‘AUTOSAVE_INTERVAL’, 86400);” !!
- on small systems redis and other cache technics can generate too additional hidden “posts” traffic to the Apache2 & SQL
- checkout the system by disable all security addons and fine tune settings, if ok enable them again..
- try wordpress cache plugins instead redis, perhaps they create more static stuff on cache and slow over uptimes by cron!