Grip loss despite 6 mm profile

Hi there, I have a short question. I have a 340i M-pack 19, but I’m not a racing driver 😉 My summer tires Bridgestone S001 Runflat have since this year ( tires are from the beginning of 2017) hardly grip (profil still close to 6mm). If I latch on at about 80 km/h times the vehicle goes into the control and points to the wheels turn off at the rear. When wet it is even worse. Last year I did not have these problems. The air pressure is ok. I drive 2.3 front e and 2.4 at the rear. Please no discussion about the air pressure. I am in the tire development and know a little about BMW tires, at least as far as the air pressure is concerned. I am also not one of the drivers who beat themselves 3 bar because of the better roll resistance, or the car drives with less pressure. I was there as a test driver a 3er with runflat without air in the tire the handling course, since none of us would have followed, no matter from 2 , 2.5 or 3 bar 🙂 That only marginally. Does anyone know this problem with the grip loss?