Problem with Physics asset


This is my first time with the Physic asset and I’ve a problem.
I’ve a vehicle, made with blender :
But the problem is with the Physic asset when i import it on Unreal.
The physic asset show me these bones.
(Roue mean Wheel in french)
For example, when I put bones spheres on “name of the Wheel” it happen nothing when I lauch the test.
The Wheel just cross landscape and didn’t interact with it but wheels work correctly.
(Of course the physic Type is kinematic.
But when I put bones spheres on “name of the Wheel”_END my vehicle make random things (it flys, or cross landscape, or other crazy things)

I call your help because I’m a beginner and I don’t know what happen.