To reproduce:

1. Download and open attached "tankgame.zip" project.
2. Enter play mode.
3. Press anywhere on terrain to set a way point for a car.
4. Notice car movement.

Expected result: car slowly moves towards the set way point.
Actual result: car behavior is very jittery and car is unable to go directly to the way point.

Workaround: Disable "Tank" gameobject. After 3 seconds it will be spawned in automatically. Then the car is stable and follows it's path.

Reproduced with: 2018.1.0b1, 2017.3.0p1, 2017.2.1p1, 2017.1.3f1, 5.6.5f1, 5.5.6f1.

Notes: Reproduces on any platform. When object with wheel colliders is instantiated later in the scene, everything works as expected.