Issues with collision not reporting hits

I’m having a few issues with getting collision to work correctly in my project, as follows:

Firstly, I have a moving ball that the player can “hit” by using the interact key. This carries out a sphere trace, which casts to the ball, and modifies the ball’s direction vector. The ball currently has a sphere static mesh, and a sphere collision component added with default settings, and it works. My question is - why do I need both the static mesh and the sphere collision components? The collision presets are set to block all on the mesh, and overlap all on the sphere collision. Removing either of these components breaks my system.

My second issue is related to hit response. I want to create a mirroring effect when the ball hits certain surfaces. I set up a simple blueprint with a cube static mesh, with the collision settings on the block all preset. I am able to generate hit events when I walk into it with my player character, but my ball always flies straight through. Any ideas?

I have included screenshots of all three collision settings below:

Sphere Collision:

Static Mesh:

mesh.JPG

Mirror:

mirror.JPG

My understanding is that by having both the ball and the mirror set to generate hit events, it should work right? What am I missing? I have tested both the ball and the mirror, and they both ARE generating hit events when colliding with my character, but not each other…