VehicleSDK, HeightField and PxVehicleIsInAir = true

I use Vehicle SDK (Physx SDK 3.4.1)
In my applicatation vehicles move on a heightfield.
Vehicle from respawn start to move well, but
at any point it can stops. And it can not begin to move anymore.
At this moment PxVehicleIsInAir returns true, but Physx Visual
Debugger shows another. PVD shows the points of
contact of the wheels with heightfield.

What should I check ?

Does pvd show a rigid body contact or a raycast hitting the heighfield? If you see a rigid body contact then the problem is easily fixed. The wheels should be supported by raycasts but not by rigid body contact. This suggests an issue with the collision filtering on the wheel shapes. They need to be configured to suppress contact.

It working! Thanks!