This is most likely just a feature, not a real bug, but I would like to see a change in this.
Right now: once espionage status reach "advanced" anything is done. I can just cap the cash down to 0 and will still get ocasionaly a stolen tech. It should "not" work that way. If we want to steal a tech, we should still invest some money.
I know we need a massive revamp of the espionage system, but this would be an easy step in the right direction.