Collisions only transform properly on the Y axis when set at an angle. Scaling on the X & Z axis causes the collision to not cover initially set areas on the parent object. As stated by the licensee it is believed that the collision is scaled locally instead of the parent object.
Result: The collision box isn't scaled to the stairs
Expected: The collision box scales to the stairs object instead of local scaling
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-52733 in the post.