Thirdly - Does it happen with 20 bots?
Fourthly - Do you do anything in the map before you unpause the bots.
(For Example: This can happen if an entity nymber is incorrect. if you build/destroy the item before unpasuing the bots and ET won't crash then that might be the action with a bad entity. Sometimes when waypointing a problem is not caught because an engineer bot doesn't chose a particular problem action at a certain point.)
LOGS:
When it crashes check to see if the files Fritzbot\etserver.log Fritzbot\etconsole.log exist. If so rename them so they won't be erased when you restart ET. There is a small chance these files may help.
This
web page show how to start logging the server and console. Be warned the console gets verbose if you do this,.