All Logins come from the IP 127.0.0.1, so if a user locks the IP out, all users get locked out, as they all have the same IP address.Add this to wp-config.php file, just ABOVE the line:/* That’s all, stop editing! Happy blogging. */

127.0.0.1 lockout fix

/** Required Code for showing correct IP address */
if(isset($_SERVER['HTTP_X_FORWARDED_FOR'])) { 
$xffaddrs = explode(',',$_SERVER['HTTP_X_FORWARDED_FOR']); 
$_SERVER['REMOTE_ADDR'] = $xffaddrs[0]; 
}