I experienced this when I first initiated the event. I didn’t have the event specific car, the 2012 Eagle Speedster. So from the same menu I bought the car, however, something glitched and I was on the loading page for the race(where you can change difficulty, tune the car, view competition etc.).
The whole series thereafter, even selecting the right car in the options, had me race in the Avendentor that I was in Free Roam.
Here are the video links:
Link1:
FH4 Bug 1
Link2:
FH4 Bug 1.1
On the side note: There is another issue, when looking at the drivatars, the club names appear as a number, visible in the video.