It's because the game (seemingly) won't listen to what I'm telling it to do. The car was corkscrewing in the air and had a lot of extra drag from parts I gave 0 drag / 0 lift. Me and @DevinXXL both tried a ton to fix behaviors like this but weren't making progress.
Unfortunate to hear! Maybe the guy who has made the Formula 1 inspired car can give you some advice. Because I think he's currently working on a new 2021 model and was able to fix some of the aerodynamic-problems the current version has!
I know it's been a few months now, but I just had a possible idea to a fix for the bugged aerodynamics. Why not give all parts of the vehicle aerodynamics similar to real cars. The body will create a bit of drag, the wheels and other will create drag, you may have to do research on the exact effects of airflow on a car like this, but this could possibly fix the issue.