I have my own dedicated server and using WHM as a control panel solution. I'm also been using CSF as a firewall protection.
For quite a while CSF locks me out when I use some of the services at once, like when I read my mail, connect to ssh and ftp.... Lately regular users are being locked out as well. Until now I managed to flush all the blocks by connecting from my mobile phone's internet connection.
There are a lot of thread out there on google when you search it but couldn't find a permanent solution.
Hope there is a solution,