Why are my AI so tentative after latest installation of GP4?

I haven't had GP4 installed for a while as I couldn't find a way to make it work with my controllers, until a few weeks ago - so I reinstalled it.

But somehow my AI are very tentative - like they give way too much space to each other - like 5 metres in Melbourne T1 - and they defend way too early - i.e. they start blocking when a car is like 60-70 metres behind them. It feels like they are detecting the other cars as much bigger "objects", if that makes sense.

I've played this game a lot and this didn't use to be their standard behaviour. I watched Ted Meat's Grand Prix 4 videos and on his gameplay, they still behave as I would expect them to.

I even tried running the game just with the GP4.exe, without CSM/GPXPatch, but the behaviour is still the same - way too timid.

I tried changing the difficulty as well, to no avail.

Has anyone else seen this behaviour in their game, and managed to find a way to fix it?