I'm using the arrow keys of my keyboard and on both tracks I'm only using the up arrow to throttle, so no left or right steering done by me at all. Tested it a dozen times to be sure I was not accidentaly touching another arrow key or any other key at all. Which wasn't. I'm going straight forward every time. I recall having the same issue in Canyon on track C03. In practice runs you didn't hear the car touch the ground right after start, while in an official race you could hear the touchdown. Or the other way around. I can't remember. But I guess that's a speed problem instead of a steering problem.
Maybe these images will help:

