Yesterday I played 2 races in the Forza Cup with Hypercars where I experienced frame drops / stuttering during the race. It was on the Le Mans race with full rain and on Suzuka with a misty environment. High speed racing is totally uncontrollable in those condition. Ok, I do get my Xbox One X in a few weeks but I guess there is a legion of players still gaming on the original One, hope you guys can fix this. It is finally one of the biggest focal points of Forza, a smoothly 60FPS gameplay.
Edit: At the Nurburgring full circuit (with Nordschleife) is also happens without rain. It occurs when the drivatars goes into the pitlane!