The annoying moment (moment meaning neverbloodyending) when you're trying to kill yourself on purpose so you can restart a mission and the AI's decide to revive you non stop. They never seem to die!

Also, when you're trying to complete a mission stealthily and they decide to shoot any cops in the street.

OR when you are trying to get hostages and they shoot them.

OR when you try to succeed a mission and are sawing into deposit boxes and the AI's decide you don't need cover so they can stand in your way as you are shot endlessly!