Sure thing!
For diplomats I don't agree; there should be some ''slow'' diplomat at home then that can negotiate in your home region because that's where the decision making happens. The one you start off with gets constant quests to get trade deals with countries and ends up far away..
Here is an example of the AI not accepting a region - tried to give HRE back Ratisborn but they don't want it back; this happened multiple times for example to get Spain to peace out I had to capture parts of Spain which I don't want to keep and they wouldn't take them back, nor would Aragon accept it as a gift nor the Moors who were my allies;
England not taking Wales in 90+ turns..
And the message that keeps appearing is Albigensian Heresy - I saw this one like 10 times; its not each turn but often enough