Another post from Turn 10 reports that the issues with Forzathon have been “FIXED”, however that is not the case.
I have exceeded the 10,000 Drift Score challenge multiple times from my Xbox One X and Xbox One without unlocking that challenge.
TO THE SLOPES!
• Get a 10,000 Drift Score n a single lap on the Bernese Alps Club Circuit Reverse
• Complete 3 Laps on the Bernese Alps Club Circuit
• Win a race in a Modern Off-Roader Division car in the Bernese Alps
Set it to drift, make it 2:30 that should be plenty, maybe more if you need two laps.
After you pass the start/finish, stop the car and wait for time to run out.
Continue prompts and go to “Next Race”
(Will also probably work with the restart option too.)
With a decent car you should be able to nearly get the score beat in the first turn alone, so don’t sweat it too much if you mess up.
Better to kill the drift and bank points than to put it into the wall/spin the car and lose the points.
I was having this exact same issue. Reading another post, I tried switching tracks to Festival Circuit Reverse. Finally got past the 10k achievement when all the above was true. Its especially important to complete the lap