I'm talking about the standard new M3, and it's not the only car. Feels like a general issue, tbh... This was with nice and hot street tires after a few laps where I started goofing off a bit and getting it wider and wider, until I hit this threshold where the car just washed out no matter what I did. This made me try the same with a few other cars and I felt the same.
Bear in mind I have a T500RS wheel and the FFB is really vague. Could be just something makes it feel weird through FFB... The FFB "fix" made it even more vague, if anything.