I have tried multiple times all that have passed the minimum requirements, using the correct vehicle, keeps says requires 1mph more for seasonal challenge.
It took me axwhile but i was able to get all of them. Had to fine tune the down force differently for each stunt though.
Mine turned out to be a tune bug. In the garage is said a800 but then on the road it said s1 801. Not sure what happened there, but with a new tune its was all ok👌
Ive had that happen before, but in Motorsport, not Horizon.