Fritzbot or Fritzbot ET?
Fritzbot has issues with anti-lag settings because
RTCW anti-lag does not work properly.
For ET how many bots and which map may be overtaxing your server. Have you tried just a couple of bots to start then add more as your friends have completed joining? Are your friends downloading to join? Other servers obviously don't have the problem since they have successfully operated for some time.
If you still can't figure it out post your server cfg so people like Nedd3h and other longtime server admins can compare notes