Collision filtering is producing unexpected results in certain setup. Objects are passing through one another when they are expected to collide.
This is quite tricky to setup. See UDN for all information
Essentially need the supplied DefaultEngine.ini file in order to get the custom collision filtering setup.
Then create a level with a floor, add an actor with two shapes one with VehicleToWorld and the other as VehicleToVehicle.
When PIE the object will fall through the ground, the VehicleToWorld collision should collide with and rest on the terrain.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-160173 in the post.