So I have a car that worked perfectly fine and then started turning the opposite direction than it was originally.
I think this is because of the changes that happened to Motor6Ds. Snippet from the devforum post:
in models that you rigged yourself or with third-party tools and happen to be using Motor6Ds “backwards”, your game may be affected. Soon they will be not-backwards, which might mean “backwards” for you.
Here’s the link: [Live] Changes to Motor6D.Transform and Motor.CurrentAngle