I’ve used 1709 and the hitching is still present for me. That’s the 1st thing I did. The only thing that fixed it for me so far is to put everything on dynamic and use recommended. While also using 60FPS vsync. Anything else causes hitching for me.
The problem with this is that it’s random. But when it does hitch it’s consistent in certain spots on the track. Sometimes when you start F7 it’s ok. Other times when you start F7 you have the hitching. It’s random. I suggest that you exit out the game go back in and try the same Dubai. As its not clear what track you used. If you able, max out all settings if you still can get 60 FPS.
Lets not forget that the previous update coincided with the Spring, April 2018 win10 update.
Edit:
Here is a thread from way back and when someone else reported the problem. Here is what was said in part
https://forums.forza.net/turn10_postst108505_Forza-7--Stuttering-fixed--AMD-1100T-w-GTX1080.aspx