Centova Cast uses a largely unmodified Pure-FTPd as its FTP server. So you are making these statements in regard to one of the most reliable, well-tested, and widely deployed FTP server applications in existence.
That's a polite way of saying that the problem is on your end.
If you're getting a "too many connections" error then the FTP server is not shutting down -- most likely something is going wrong between you and the server. You would need to check your syslog to see what Pure-FTPd reports is going wrong.
If all else fails you can set FTP_OPTIONS="-d -d" in /usr/local/centovacast/etc/cc-ftpd.conf to have the entire FTP conversations logged to syslog.