Why is physic simulation on fbx exported from blender bugged?

Hello

i have a Problem with getting physics to work properly…

i created a simple boned rig in latest Blender version and exported it to UE4…

but as you can see in the video the physics goes crazy and i dont know why…

i also tried to make the colussion spheres smaller but with no success…my mesh still moves rapidly without any reason :frowning:

anybody could help?