I added a vehicle by adding the basic vehicle, and then adding a skeletal mesh to it. This works great and the car drives as expected.
I bought a car pack and switched the skeletal mesh to one from the pack (I’ve tried several with the same result) and when I run my simulation the car bounces up off the road, and then rotates around it’s center, dropping the back wheels to the ground and lifting the front in the air.
The only difference is the skeletal mesh… I’ve reached out to the creator of the pack… but is there anything I could look at that might cause this?