Fix Fail2Ban "Cannot add a custom filter to fail2ban"
There is a known issue in the fail2ban UI where filters don't show up if they are missing the "ignoreregex" property:
Thank you for reporting this bug, we have confirmed it (bug ID for your reference: PPPM-7718). Note: only feature requests are allowed here, so we would appreciate if you post bugs and issues on our forum at https://talk.plesk.com. We are closing this request since it does not contain any feature suggestions.