Check your browser’s web developer tools in the Network tab to see what the response code is when you try to save the form. I suspect you’ll see a 4xx code. My best guess is that your server has a security toolset like mod_security that mistakenly thinks that the ( is an attempt to attack the server, and is preventing the form from being saved.
Parentheses aren’t UTF-8 multibyte characters, so I don’t think the UTF8 configuration is part of the problem.
Regards,
Alec Smecher
Public Knowledge Project Team