AI doesn't takes original bid when modified.
Steve the Conqueror
When modifying a trade with the AI, the AI accepts the original trade terms rather than the modified trade.
For instance, if the AI tries to trade a wheat for a rock and you change it for a sheep and a wheat for that rock, when the AI accepts it, it will only trade the wheat and rock. Happened to me at least 4 times in the last few days. v. 1.9.0, I have a video capture of this too.