I am in a case almost similar:
I am implementing some Components derived from the SceneComponent.
This component was previously derived from ActorComponent. Which does not offer the ability to hook anything on it. But the meshes it was creating on the parent were working.
From the moment I changed to SceneComponent (in the hope of attaching the meshes I was creating in the actor to this component), all the collisions stopped working.
It seems that anything that gets attached to a SceneComponent gets its collisions canceled.
I think that this has to do with something like “no sweep on the childs of SceneComponents” or something of the like. I will try to investigate a bit the C++ but without knowing what and where to search. I doubt I could find anything. 
Any answer would be welcome.