If you are going down a steep incline all the weight of the car is forward unweighting the back making it easy to spin. Seemingly odd things can happen on inclines. For example, Limerock park has a hill when you crest the hill weight comes off the front wheels if your wheels aren't straight when the weight comes back down, your can lose control of the car. This happens in both iRacing and rF2.
I know exactly the place at Limerock you're talking about GT11, used to give me fits until I learned to let off the gas just a touch as the back wheels came down
, I think it did the same thing in Race 07 too depending on the car but wasn't quite as severe as in iRacing.
Some of the corners at Matterhorn and Bathrust have been giving me fits too, I think it's mostly me going in too fast and causing myself problems with spins or just understeering into walls because I'm just unfamiliar with the nuances of the tracks yet.