I've just noticed that since the latest update (1.12 PS4) the AI are doing some strange things with their pit stops. I did two races with the Career Mode at Austria and Silverstone this weekend, and most of the AI are changing to the hard tyre instead of the medium tyre at their pit stop. Just did a 25% Career Mode Race at Silverstone. The AI started at the softs but they pitted after 9 of 13 laps to change to the hard tyres. Before the latest patch they did just normal pitstops and changes to the medium tyres. It's a shame, because it destroyes some good races against the AI, because they are really slow on the hard tyre.