The collision of the cube static mesh is not blocking the character after Setting World Scale 3D while it is attached to another actor using the AttachToActor node.
1. Open the attached project
2. PIE
3. Press 1 to scale the top cube
4. Walk under the scaled cube
5. Jump a few times into the bottom of the cube
Result: After a few jumps (the exact number varies) your character will pop through the collision and be able to walk inside of the cube.
Expected: The collision would block the character.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-31660 in the post.