I know this is a known issue but just for the record I just lost my front wing when an AI with plenty of room around it hit the brakes (or lifted off) about 3-400 metres (i.e. way out) from the first chicane at Monza, It felt like they were looking too far ahead saw some traffic and hit the brakes. It was happening a bit around the track especially in the early laps. The above incident was about lap 3 and the field had spread out. I was set to Get Real, AI = 102, 33 AI opponents and started in 29th.
Replicated this morning: You can see two short clips in the video... 1) approaching Ascari - I am 'holding station' at equal top speed behind the AI car in front. He then slows or brakes early and I almost hit him and brake hard myself. We are still well short of the usual braking point (AI=102, default set ups, lap 2). 2) from Parabolica to first chicane - I am way behind and 'holding station' at roughly equal speed - then all of a sudden I am weaving through the field that has slowed down. Not under yellow. No incidents. AI=102, default set ups, lap 3.
I have observed the same behaviour with the WTCR cars as well. I don't remember the settings, but it does it all the time, every lap.
WTCR 2018, Adaptive AI That behaviour doesn't happen for every AI car, but it still does it quite often. As you can see, they also brake quite a bit earlier than needed.