To reproduce:
1. Open attached project
2. Open test4 scene
3. Enter play mode
4. make the car flip (continuously holding w + a will do the trick)
5. Observe
Expected result: it rolls over
Actual result: After almost finishing to roll over it jumps upwards
Note: I suspect this happens because upon turning fully around the wheel collider detects itself as being very close to the ground, thus it applies huge spring force which causes the jump.

By Design:
There is nothing we can do to it as of right now. The raycast car model just has this limitation, and one can only approach it from the content side of things, not the algorithm one. This can be improved when we enable shape sweeps instead of raycasts, but that's unclear when happens.
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Some of the ways to work this around are:
1) Use EasySuspension to configure cars to make sure the springs are not excessively stiff. This also helps to make the car follow the uneven surface smoother as the wheel bumps won't result in high forces setting the car to air.

2) Protect the places where the wheels are installed by additional colliders to exclude this situation where the car flips on the side until the wheel collider touches the ground to set the car into the air. Having those colliders is also important to make wheels push the smaller colliders out of the way.