Not sure what you mean. If you mean that the AI is constantly moving you to new targets, yes -- it'll do that, and it can indeed be annoying when you're playing as a councillor to an AI overlord. It has nothing to do with the target being impossible.
I mean, the AI was trying to have me improve relations on a theocracy instead of the court chaplain. The AI may behave differently in how it executes things (not checking for government, so it'll just execute the command over and over until it gets bored and finally settles on a viable government), but chancellors can't be used to improve relations on a theocracy.