On multiple occasions on multiple course in a full range of vehicles from slow to bullet fast I've seen the following:
AI pitting each other or me.
AI exiting a turn very slowly then coming to a complete stop in the middle of the track before taking off again.
AI exiting a turn very slowly then just coasting or getting stuck in one gear.
AI driving straight into a barrier off course and staying there the entire race.
Pass first to take the lead, finish the race, AI I just passed, now in 2nd place, is marked as 1 lap down but 3rd onward have valid times.
AI brake checking me so often I'd try to knock out someone in the pits after the race.
AI punting me off course.
AI driving completely passively until passed then retaliating by pit or punt.
The AI in GT6 is abysmal almost all the time but every once in a while shows a glimmer of promise then procedes to coast or stop or something as equally stupid.
Unless PD performs a miracle on GT6 I'm done with Gran Turismo and PD.
Sark